sql/catalog/lease: optimize descriptor leasing protocol for cold start

[ajwerner]

Is your feature request related to a problem? Please describe.
In order to use tables for DML queries, sql servers need to acquire leases for the underlying descriptors. The process of acquiring a lease on a descriptor required a number of KV operations:

• Read the namespace table to find the descriptor
• Read the descriptor
• Read and validate the cross-references for the descriptor
• Write the lease entry

Today, each of these operations will potentially leave the current region. We'd like it to be the case that we can acquire leases without leaving the current region.

Describe the solution you'd like
We ought to leverage a combination of LOCALITY GLOBAL and LOCALITY REGIONAL BY ROW configurations for the relevant system tables.

Describe alternatives you've considered
We could attempt to avoid the LOCALITY GLOBAL configuration on the system.descriptors table if we used some other causality propagation mechanism. It's probably not worth the trouble.

Additional context

The above leasing protocol is also used to cache password hashes, role membership, and virtual privileges. Those system will benefit transparently from the above work.

This work depends on being able to configure system tables with MR primitives (currently tracked in #63365).

Epic: CRDB-18596

Jira issue: CRDB-18414

[ajwerner]

We've done this for multi-tenant deployments within secondary tenants which are opted into multi-region functionality.

[ajwerner]

The following work implements this originally:

• Use KV to write to system.lease: sql/catalog/lease: switch lease manager to use KVs, lease system tables in SQL  #90530
• Partition the lease table: sql: partition lease table when optimizing system database for MR #93342
• Set up the system database multiregionccl: add unsafe_optimize_system_database #92395
• Set up the lease table: lease,systemschema: hook up the lease table to regional-by-row partitioning #92588
• Migrate the lease table: lease: migrate lease to rbr compatible index #98446