release-21.2: kvserver: log if lease applies with a delay

[blathers-crl]

Backport 1/1 commits from #96257 on behalf of @tbg.

/cc @cockroachdb/release

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When we transfer a lease to a lagging follower, there's often a latency
blip that we get asked to investigate. This is time consuming; it's
often very subtle to even figure out that it happened. We try to be
better about not doing it, but at least on 22.1 we know it's possible,
and we can't backport the rather involved fixes.

This warning makes it fairly obvious when it happens.

W230131 [...] [T1,n2,s2,r23/3:‹/Table/2{1-2}›,raft] 165 lease repl=(n2,s2):3 seq=5 start=1675153630.108829000,0 epo=3 pro=1675153630.108829000,0 active after replication lag of ~0.58s; foreground traffic may have been impacted [prev=repl=(n3,s3):2 seq=4 start=1675153407.528408000,0 epo=2 pro=1675153419.837642000,0]

Addresses #95991.

Epic: none
Release note: None

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Release justification:

[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]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

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

[cockroach-teamcity]

This change is 

[erikgrinaker]

21.2 is no longer maintained.