release-22.2.0: metrics: add tsdb persistence to AggHistogram

[dhartunian]

Backport 1/1 commits from #90769.

/cc @cockroachdb/release

---

Previously, AggHistogram instances would not persist their quantiles to tsdb due to a missing interface implementation of metrics.WindowedHistogram. This PR adds a trivial implementation that delegates to the aggregate histogram instance within the struct.

This is relatively safe to do even though an AggHistogram could contain many children because we are only exporting a single set of aggregate quantiles per-AggHistogram. The children are only iterated over via the PrometheusIterable interface which is used by the prometheus exporter, but not by the metrics recorder.

NOTE: This backported commit includes a test fix to the kv package that was
lifted from #88076.

Release note (bug fix, ops change): Previously, certain aggregate histograms would appear in _status/vars but not be available for graphing in the DB Console. These are now made available. They include changefeed-related histograms, and row-level-TTL histograms.

Epic: None

Release Justification: Category 3: Fixes for high-priority or high-severity bugs in existing functionality

[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 

[abarganier]

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @rafiss)

[nkodali]

Reviewed 1 of 1 files at r1, all commit messages.
Reviewable status: complete! 2 of 0 LGTMs obtained (waiting on @rafiss)

[dhartunian]

Added port of test fixes from #88076 and added a note to that regard to PR+commit.