kvserver: remove ad-hoc queue stats from RaftTransport

[pav-kv]

trafficstars

These stats are only printed in text to the logs. There is a queue size metric introduced in 5d51ab34 which properly exports these stats to monitoring. The exported graphs allow observing both the current, and historical queue sizes (including the max size).

This commit removes the queue and queueMax stats as obsolete.

Part of #83917

Release note: None

[cockroach-teamcity]

This change is 

[pav-kv]

@ajwerner This removes your TODO because it's no longer relevant after this PR: we reduce the granularity of counters. Is it fine, or you would still leave/reword the TODO?

[pav-kv]

bors r=tbg

[craig[bot]]

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• Bazel Essential CI (Cockroach)

[craig[bot]]

Build succeeded:

• Bazel Essential CI (Cockroach)