release-23.1: server: deflake test hot ranges response

[koorosh]

Backport 1/1 commits from #99108.

/cc @cockroachdb/release

---

Flaky tests for HotRanges api were caused after changing source
for getting stats per replica in mapToHotReplicasInfo func.
mapToHotReplicasInfo func calls Repl().LoadStats() that
internally relies on calculates average values per second
in current moment, but values could be recorded earlier.

Now, mapToHotReplicasInfo func relies on RangeUsageInfo() func
that keeps average stats at the time stats were recorded.

Related change to this fix: #99716

Release note: None

Fixes: #98619

Release justification: non-production code changes

[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?

[blathers-crl]

Thank you for contributing to CockroachDB. Please ensure you have followed the guidelines for creating a PR.

My owl senses detect your PR is good for review. Please keep an eye out for any test failures in CI.

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[cockroach-teamcity]

This change is 

[maryliag]

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @gtr, @j82w, @kvoli, @THardy98, @xinhaoz, and @zachlite)