release-23.2: sql: collect table statistics on virtual computed columns

[michae2]

Backport:

• 2/2 commits from "sql: collect table statistics on virtual computed columns" (sql: collect table statistics on virtual computed columns #118241)
• 1/1 commits from "sql: guard against non-public mutation columns in CREATE STATISTICS" (sql: guard against non-public mutation columns in CREATE STATISTICS #118930)

Please see individual PRs for details.

/cc @cockroachdb/release

Release justification: high priority business need for the functionality which cannot wait until the next release.

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
• Backports should not break backwards-compatibility.
• Backports should change as little code as possible.
• Backports should not change on-disk formats or node communication protocols.
• Backports should not add new functionality (except as defined
  here).
• Backports must not add, edit, or otherwise modify cluster versions; or add version gates.
• All backports must be reviewed by the owning areas TL and one additional
  TL. For more information as to how that review should be conducted, please consult the backport
  policy.

If your backport adds new functionality, please ensure that the following additional criteria are satisfied:

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters. State changes must be further protected such that nodes running old binaries will not be negatively impacted by the new state (with a mixed version test added).
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.
• Your backport must be accompanied by a post to the appropriate Slack
  channel (#db-backports-point-releases or #db-backports-XX-X-release) for awareness and discussion.

Also, please add a brief release justification to the body of your PR to justify this
backport.

[cockroach-teamcity]

This change is 

[michae2]

Are all of the changes protected via a flag or option, new syntax, an environment variable or default-disabled cluster setting?

Yes, all of the changes are behind cluster setting sql.stats.virtual_computed_columns.enabled which is disabled by default in these backports.

What are the risks to backporting this change? Can the risks of backporting be mitigated?

Main risk is that with sql.stats.virtual_computed_columns.enabled turned on we build an invalid distsql plan for stats collection, which could prevent statistics collection on some tables if it were to happen.

What are the risks to not backporting?

Statistics estimates for queries on indexed virtual computed columns will continue to be inaccurate, possibly prohibiting creation of indexes on virtual computed columns.

Does this change really need to be backported? Or can it reasonably wait until the next major release to be addressed?

It cannot wait.

[michae2]

The backport was clean, there were only minor differences from master:

• sql.stats.virtual_computed_columns.enabled is false by default
• had to add SET CLUSTER SETTING sql.stats.virtual_computed_columns.enabled = true to distsql_stats and distsql_misc logic tests

[michae2]

One failure is unrelated flake #120817. I'll look into the other failure this morning.

[michae2]

Extended CI failure is a flake, this is RFAL.