release-24.2: kvcoord: log replica order on nearest routing policy

[blathers-crl]

Backport 2/2 commits from #129264 on behalf of @kvoli.

/cc @cockroachdb/release

---

Previously, we would log an event when routing to the nearest replica,
which would then show up in traces and could be used to determine the
routing policy of a query.

It is also useful to know how the nearest replica was selected i.e.,
latency, locality or by health. Log the event after sorting by the
replicas' distance to the sender and include the replica order.

Informs: #129031
Release note: None

---

Release justification: Observability change to make debugging follower reads easier. Disabled unless tracing.

[blathers-crl]

Thanks for opening a backport.

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[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?

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[cockroach-teamcity]

This change is