release-23.1: kvserver: add metrics for raft (re-)proposals

[pav-kv]

Backport 1/1 commits from #111272.

/cc @cockroachdb/release

---

This commit adds new metrics:

• raft.commands.proposed: commands proposed to Raft by leaseholders
• raft.commands.reproposed.unchanged: commads retried/reproposed to Raft because they take too long to apply (so they might be dropped)
• raft.commands.reproposed.new-lai: commands retried/reproposed to Raft because they were committed to Raft out of order (failed the LAI or closed timestamp check)

The proposed metric includes both reproposed metrics.

Resolves #105199
Epic: none
Release note (ops change): added metrics for raft proposals and reproposals

Release justification: observability improvement for support escalations

[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]

Approving based on:

critical gaps in an operators' ability to detect and troubleshoot serious issues in their clusters

Will need an additional non-KV TL review, as well as a post in #db-backports-point-releases, as per the backport policy.

[pav-kv]

@jbowens Could you please take a look if this is good to backport to 23.1? This change backports a few metrics useful for L2.

[jbowens]

lgtm