sql: support tenant creation and deletion, track in system.tenants table

Most of cockroachdb#47904.

First commit from cockroachdb#48504.
Second and third commit from cockroachdb#48773.

This commit implements the initial structure for tenant creation and
deletion. It does so by introducing a new system table to track tenants
in a multi-tenant cluster and two new builtin functions to manipulate
this table and the overall multi-tenant state.

The change starts by introducing a new `system.tenants` table with the
following schema:
```
CREATE TABLE system.tenants (
    id     INT8 NOT NULL PRIMARY KEY,
    active BOOL NOT NULL DEFAULT true,
    info   BYTES
);
```

The `id` column is self-explanatory. The `active` column is used to
coordinate tenant destruction in an asynchronous job. The `info` column
is an opaque byte slice to allow users to associate arbitrary
information with specific tenants. I don't know exactly how this third
field will be used (mapping tenants back to CockroachCloud user IDs?),
but it seems like a good idea to add some flexibility since we do intend
to eventually expose this externally.

The table is given an ID of 8, which means that it falls within the
"system config span". I believe this is ok, because the entire concept
of the "system config span" should be going away with cockroachdb#47150. The table
is also only exposed to the system-tenant and is never created for
secondary tenants.

The change then introduces two new builtin functions:
`crdb_internal.create_tenant` and `crdb_internal.destroy_tenant`. These
do what you would expect - creating and destroying tenant keyspaces,
along with updating metadata in system.tenants.

docs/generated/sql/functions.md

@@ -1114,6 +1114,19 @@ has no relationship with the commit order of concurrent transactions.</p>
 </span></td></tr></tbody>
 </table>
 
+### Multi-tenancy functions
+
+<table>
+<thead><tr><th>Function &rarr; Returns</th><th>Description</th></tr></thead>
+<tbody>
+<tr><td><a name="crdb_internal.create_tenant"></a><code>crdb_internal.create_tenant(id: <a href="int.html">int</a>) &rarr; <a href="int.html">int</a></code></td><td><span class="funcdesc"><p>Creates a new tenant with the provided ID. Must be run by the System tenant.</p>
+</span></td></tr>
+<tr><td><a name="crdb_internal.create_tenant"></a><code>crdb_internal.create_tenant(id: <a href="int.html">int</a>, info: <a href="bytes.html">bytes</a>) &rarr; <a href="int.html">int</a></code></td><td><span class="funcdesc"><p>Creates a new tenant with the provided ID. Must be run by the System tenant.</p>
+</span></td></tr>
+<tr><td><a name="crdb_internal.destroy_tenant"></a><code>crdb_internal.destroy_tenant(id: <a href="int.html">int</a>) &rarr; <a href="int.html">int</a></code></td><td><span class="funcdesc"><p>Destroys a tenant with the provided ID. Must be run by the System tenant.</p>
+</span></td></tr></tbody>
+</table>
+
 ### Sequence functions
 
 <table>

pkg/cli/testdata/zip/partial1

@@ -217,7 +217,7 @@ requesting database details for defaultdb... writing: debug/schema/defaultdb@det
 requesting database details for postgres... writing: debug/schema/[email protected]
 0 tables found
 requesting database details for system... writing: debug/schema/[email protected]
-26 tables found
+27 tables found
 requesting table details for system.comments... writing: debug/schema/system/comments.json
 requesting table details for system.descriptor... writing: debug/schema/system/descriptor.json
 requesting table details for system.eventlog... writing: debug/schema/system/eventlog.json
@@ -240,6 +240,7 @@ requesting table details for system.statement_bundle_chunks... writing: debug/sc
 requesting table details for system.statement_diagnostics... writing: debug/schema/system/statement_diagnostics.json
 requesting table details for system.statement_diagnostics_requests... writing: debug/schema/system/statement_diagnostics_requests.json
 requesting table details for system.table_statistics... writing: debug/schema/system/table_statistics.json
+requesting table details for system.tenants... writing: debug/schema/system/tenants.json
 requesting table details for system.ui... writing: debug/schema/system/ui.json
 requesting table details for system.users... writing: debug/schema/system/users.json
 requesting table details for system.web_sessions... writing: debug/schema/system/web_sessions.json

pkg/cli/testdata/zip/partial1_excluded

@@ -154,7 +154,7 @@ requesting database details for defaultdb... writing: debug/schema/defaultdb@det
 requesting database details for postgres... writing: debug/schema/[email protected]
 0 tables found
 requesting database details for system... writing: debug/schema/[email protected]
-26 tables found
+27 tables found
 requesting table details for system.comments... writing: debug/schema/system/comments.json
 requesting table details for system.descriptor... writing: debug/schema/system/descriptor.json
 requesting table details for system.eventlog... writing: debug/schema/system/eventlog.json
@@ -177,6 +177,7 @@ requesting table details for system.statement_bundle_chunks... writing: debug/sc
 requesting table details for system.statement_diagnostics... writing: debug/schema/system/statement_diagnostics.json
 requesting table details for system.statement_diagnostics_requests... writing: debug/schema/system/statement_diagnostics_requests.json
 requesting table details for system.table_statistics... writing: debug/schema/system/table_statistics.json
+requesting table details for system.tenants... writing: debug/schema/system/tenants.json
 requesting table details for system.ui... writing: debug/schema/system/ui.json
 requesting table details for system.users... writing: debug/schema/system/users.json
 requesting table details for system.web_sessions... writing: debug/schema/system/web_sessions.json

pkg/cli/testdata/zip/partial2

@@ -153,7 +153,7 @@ requesting database details for defaultdb... writing: debug/schema/defaultdb@det
 requesting database details for postgres... writing: debug/schema/[email protected]
 0 tables found
 requesting database details for system... writing: debug/schema/[email protected]
-26 tables found
+27 tables found
 requesting table details for system.comments... writing: debug/schema/system/comments.json
 requesting table details for system.descriptor... writing: debug/schema/system/descriptor.json
 requesting table details for system.eventlog... writing: debug/schema/system/eventlog.json
@@ -176,6 +176,7 @@ requesting table details for system.statement_bundle_chunks... writing: debug/sc
 requesting table details for system.statement_diagnostics... writing: debug/schema/system/statement_diagnostics.json
 requesting table details for system.statement_diagnostics_requests... writing: debug/schema/system/statement_diagnostics_requests.json
 requesting table details for system.table_statistics... writing: debug/schema/system/table_statistics.json
+requesting table details for system.tenants... writing: debug/schema/system/tenants.json
 requesting table details for system.ui... writing: debug/schema/system/ui.json
 requesting table details for system.users... writing: debug/schema/system/users.json
 requesting table details for system.web_sessions... writing: debug/schema/system/web_sessions.json

pkg/cli/testdata/zip/specialnames

@@ -21,7 +21,7 @@ requesting table details for defaultdb.pg_catalog.pg_class... writing: debug/sch
 requesting database details for postgres... writing: debug/schema/[email protected]
 0 tables found
 requesting database details for system... writing: debug/schema/[email protected]
-26 tables found
+27 tables found
 requesting table details for system.comments... writing: debug/schema/system-1/comments.json
 requesting table details for system.descriptor... writing: debug/schema/system-1/descriptor.json
 requesting table details for system.eventlog... writing: debug/schema/system-1/eventlog.json
@@ -44,6 +44,7 @@ requesting table details for system.statement_bundle_chunks... writing: debug/sc
 requesting table details for system.statement_diagnostics... writing: debug/schema/system-1/statement_diagnostics.json
 requesting table details for system.statement_diagnostics_requests... writing: debug/schema/system-1/statement_diagnostics_requests.json
 requesting table details for system.table_statistics... writing: debug/schema/system-1/table_statistics.json
+requesting table details for system.tenants... writing: debug/schema/system-1/tenants.json
 requesting table details for system.ui... writing: debug/schema/system-1/ui.json
 requesting table details for system.users... writing: debug/schema/system-1/users.json
 requesting table details for system.web_sessions... writing: debug/schema/system-1/web_sessions.json

pkg/cli/testdata/zip/testzip

@@ -91,7 +91,7 @@ requesting database details for defaultdb... writing: debug/schema/defaultdb@det
 requesting database details for postgres... writing: debug/schema/[email protected]
 0 tables found
 requesting database details for system... writing: debug/schema/[email protected]
-26 tables found
+27 tables found
 requesting table details for system.comments... writing: debug/schema/system/comments.json
 requesting table details for system.descriptor... writing: debug/schema/system/descriptor.json
 requesting table details for system.eventlog... writing: debug/schema/system/eventlog.json
@@ -114,6 +114,7 @@ requesting table details for system.statement_bundle_chunks... writing: debug/sc
 requesting table details for system.statement_diagnostics... writing: debug/schema/system/statement_diagnostics.json
 requesting table details for system.statement_diagnostics_requests... writing: debug/schema/system/statement_diagnostics_requests.json
 requesting table details for system.table_statistics... writing: debug/schema/system/table_statistics.json
+requesting table details for system.tenants... writing: debug/schema/system/tenants.json
 requesting table details for system.ui... writing: debug/schema/system/ui.json
 requesting table details for system.users... writing: debug/schema/system/users.json
 requesting table details for system.web_sessions... writing: debug/schema/system/web_sessions.json

pkg/keys/constants.go

@@ -332,6 +332,7 @@ const (
 	ZonesTableID               = 5
 	SettingsTableID            = 6
 	DescIDSequenceID           = 7
+	TenantsTableID             = 8
 
 	// IDs for the important columns and indexes in the zones table live here to
 	// avoid introducing a dependency on sql/sqlbase throughout the codebase.

pkg/sql/conn_executor.go

@@ -1938,11 +1938,12 @@ func (ex *connExecutor) initEvalCtx(ctx context.Context, evalCtx *extendedEvalCo
 	*evalCtx = extendedEvalContext{
 		EvalContext: tree.EvalContext{
 			Planner:            p,
-			Sequence:           p,
-			SessionData:        ex.sessionData,
-			SessionAccessor:    p,
 			PrivilegedAccessor: p,
+			SessionAccessor:    p,
 			ClientNoticeSender: p,
+			Sequence:           p,
+			Tenant:             p,
+			SessionData:        ex.sessionData,
 			Settings:           ex.server.cfg.Settings,
 			TestingKnobs:       ex.server.cfg.EvalContextTestingKnobs,
 			ClusterID:          ex.server.cfg.ClusterID(),

pkg/sql/distsql/server.go

@@ -316,10 +316,11 @@ func (ds *ServerImpl) setupFlow(
 			// ProcessorBase. StartInternal().
 			Context:            ctx,
 			Planner:            &sqlbase.DummyEvalPlanner{},
-			SessionAccessor:    &sqlbase.DummySessionAccessor{},
 			PrivilegedAccessor: &sqlbase.DummyPrivilegedAccessor{},
-			Sequence:           &sqlbase.DummySequenceOperators{},
+			SessionAccessor:    &sqlbase.DummySessionAccessor{},
 			ClientNoticeSender: &sqlbase.DummyClientNoticeSender{},
+			Sequence:           &sqlbase.DummySequenceOperators{},
+			Tenant:             &sqlbase.DummyTenantOperator{},
 			InternalExecutor:   ie,
 			Txn:                leafTxn,
 		}