release-22.2: catalog: don't set modification time for offline descriptors

[blathers-crl]

Backport 1/1 commits from #111820 on behalf of @rafiss.

/cc @cockroachdb/release

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There is a post-deserialization change that automatically sets the
modification time for all descriptors if it is not present. Notably,
there is also a cluster upgrade step that rewrites all descriptors with
post-deserialization changes, and bumps their version.

If a RESTORE is running during an upgrade, the descriptors it tries to
rewrite could have been also bumped by the upgrade step. That
would cause the RESTORE to fail.

Now, the change to automatically set the modification time is disabled
if the descriptor is on the offline state, as it is during RESTORE.

fixes #109976

Release note (bug fix): Fixed a bug that could prevent RESTORE from
working if it was performed during a cluster upgrade.

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Release justification: bug fix

[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?

[cockroach-teamcity]

This change is 

[rafiss]

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

No, since this is a bug fix.

What are the risks to backporting this change? Can the risks of backporting be mitigated? What are the risks to not backporting?

Risk of backporting: Something during the RESTORE process may have been relying on the ModificationTime being set without us knowing.
Risk of not backporting: RESTOREs during upgrades can fail; the corresponding test will keep flaking.

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

If we want to fix the bug and the test, then yes it needs to be.