release-23.1: schematelemetry: emit metrics and logs about invalid objects

[blathers-crl]

Backport 1/1 commits from #108559 on behalf of @chrisseto.

/cc @cockroachdb/release

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Short of continuously polling crdb_internal.invalid_objects, there was not a convenient way to monitor a cluster for descriptor corruption.

Having such an indicator would allow customers to perform preflight checks ahead of upgrades to avoid being stuck in a mixed version state. It would also allow CRL to more easily monitor cloud clusters for corruptions in the wild.

This commit updates the schematelemetry job to additionally update the sql.schema.invalid_objects gauge and emit logs for any encountered corruptions.

Informs: #104266
Epic: CRDB-28665

Release note (ops change): Added a new sql.schema.invalid_objects gauge
metric. This gauge is periodically updated based on the schedule set by
the sql.schema.telemetry.recurrence cluster setting. When it is updated,
it counts the number of schema objects (tables, types, schemas, databases,
and functions) that are in an invalid state according to CockroachDB’s
internal validation checks. This metric is expected to be zero in a healthy
cluster, and if it is not, it indicates that there is a problem that must
be repaired.

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Release justification: low risk addition to metrics

[cockroach-teamcity]

This change is 

[rafiss]

blathers backport 23.1.9-rc

[blathers-crl]

Encountered an error creating backports. Some common things that can go wrong:

1. The backport branch might have already existed.
2. There was a merge conflict.
3. The backport branch contained merge commits.

You might need to create your backport manually using the backport tool.

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error setting assignees, but backport branch blathers/backport-release-23.1.9-rc-109733 is ready: POST https://api.github.com/repos/cockroachdb/cockroach/issues/109739/assignees: 404 Not Found []

Backport to branch 23.1.9-rc failed. See errors above.

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[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Patches should only be created for serious issues or test-only changes.
• Patches should not break backwards-compatibility.
• Patches should change as little code as possible.
• Patches should not change on-disk formats or node communication protocols.
• Patches should not add new functionality.
• Patches must not add, edit, or otherwise modify cluster versions; or add version gates.

If some of the basic criteria cannot be satisfied, ensure that the exceptional criteria are satisfied within.

• 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.
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.

Add a brief release justification to the body of your PR to justify this backport.

Some other things to consider:

• What did we do to ensure that a user that doesn’t know & care about this backport, has no idea that it happened?
• Will this work in a cluster of mixed patch versions? Did we test that?
• If a user upgrades a patch version, uses this feature, and then downgrades, what happens?