PR #96514 - pkg/util/metric: optionally reintroduce legacy hdrhistogram model

[cockroach-teamcity]

Exalate commented:

Related PR: cockroachdb/cockroach#96514
Commit: cockroachdb/cockroach@44d0ffa

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Release note (ops change): Histogram metrics can now optionally
use the legacy HdrHistogram model by setting the environment var
COCKROACH_ENABLE_HDR_HISTOGRAMS=true on CockroachDB nodes.
Note that this is not recommended unless users are having
difficulties with the newer Prometheus-backed histogram model.
Enabling can cause performance issues with timeseries databases
like Prometheus, as processing and storing the increased number
of buckets is taxing on both CPU and storage. Note that the
HdrHistogram model is slated for full deprecation in upcoming
releases.

Jira Issue: DOC-6870