PR #83991 - kvserver: delegate snapshots to followers

[cockroach-teamcity]

Exalate commented:

Related PR: cockroachdb/cockroach#83991
Commit: cockroachdb/cockroach@760aedb

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Release note (performance improvement): Adds delegated snapshots which
can reduce WAN traffic for snapshot movement. If there is another
replica for this range with a closer locality than the delegate, the
leaseholder will attempt to have that delegate send the snapshot. This
is particularly useful in the case of a decommission of a node where
most snapshots are transferred to another replica in the same locality.

Jira Issue: DOC-6850