changefeedccl: update tests to random tenant random sink

Previously most of our tests did not run on tenants as it was not
ergonomic to do so given our helpers.  We would also manually run tests
across multiple sinks even if the test did not care about what sink it
was ran on, drastically increasing the execution time of our test suite.

This PR updates our helper infrastructure to use a shared TestServer
struct that allows access to both the system and secondary tenant
interfaces, and by default runs tests on a random sink.

It also fixes a bug in the Webhook and Cloudstorage testfeeds where
>53bit numbers were rounded off due to JSON parsing.

Release note: None

pkg/ccl/changefeedccl/BUILD.bazel

@@ -138,7 +138,6 @@ go_test(
         "changefeed_test.go",
         "encoder_test.go",
         "event_processing_test.go",
-        "helpers_tenant_shim_test.go",
         "helpers_test.go",
         "main_test.go",
         "name_test.go",
@@ -173,7 +172,6 @@ go_test(
         "//pkg/cloud",
         "//pkg/cloud/impl:cloudimpl",
         "//pkg/clusterversion",
-        "//pkg/config",
         "//pkg/gossip",
         "//pkg/jobs",
         "//pkg/jobs/jobspb",
@@ -182,17 +180,14 @@ go_test(
         "//pkg/kv/kvclient/kvcoord",
         "//pkg/kv/kvserver",
         "//pkg/kv/kvserver/kvserverbase",
-        "//pkg/kv/kvserver/liveness/livenesspb",
         "//pkg/kv/kvserver/protectedts",
         "//pkg/kv/kvserver/protectedts/ptpb",
         "//pkg/roachpb",
-        "//pkg/rpc",
         "//pkg/security/securityassets",
         "//pkg/security/securitytest",
         "//pkg/security/username",
         "//pkg/server",
         "//pkg/server/serverpb",
-        "//pkg/server/status",
         "//pkg/server/telemetry",
         "//pkg/settings/cluster",
         "//pkg/spanconfig",
@@ -241,7 +236,6 @@ go_test(
         "//pkg/util/randutil",
         "//pkg/util/retry",
         "//pkg/util/span",
-        "//pkg/util/stop",
         "//pkg/util/syncutil",
         "//pkg/util/timeutil",
         "//pkg/util/timeutil/pgdate",