release-22.2: storage: Fix GCBytesAge in CheckSSTConflicts with range keys

[blathers-crl]

Backport 1/1 commits from #88578 on behalf of @itsbilal.

/cc @cockroachdb/release

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Change #87303 fixed GCBytesAge in CheckSSTConflicts for points, but not for range keys. This change fixes it for range keys too, by ensuring the changes to statsDiff happen at the right timestamp using statsDiff.AgeTo.

Fixes #82920.

Release note: None.

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Release justification: fixes bug in MVCC stats update.

[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 

[erikgrinaker]

The backport freeze went into effect yesterday, so I'm afraid this will have to wait until 22.2.1. We're not currently expecting SSTs with CheckSSTConflicts to contain range keys anyway, so that seems fine, and if we were to start using them in mixed 23.1/22.2.0 clusters then a stats mismatch isn't the end of the world.

[github-actions]

Reminder: it has been 3 weeks please merge or close your backport!

[erikgrinaker]

I think we can get this merged now @itsbilal.

[github-actions]

Reminder: it has been 3 weeks please merge or close your backport!

[erikgrinaker]

I'm gonna go ahead and merge this.