cockroachdb: remove obsolete compactor metrics

[jbowens]

What does this PR do?

Removes metadata and reference to CockroachDB timeseries metrics that have not been exported by CockroachDB versions in many years (~v21.1).

Motivation

The documentation of these metrics is likely to confuse users.

Additional Notes

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Changelog entries must be created for modifications to shipped code
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
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[iliakur]

@jbowens 👋 thanks for the contribution!

Removing metrics from metadata.csv is something we try to avoid. That file shows up in the Datadog UI for all versions of the integration. The thing we tend to do is mark metrics as Deprecated if we stop submitting them in some version of the integration.

As for the metrics themselves, would it be possible to include some conditional that skips them if we detect a certain version of cockroachdb? With the current changeset the next release of our integration essentially drops support for certain older versions of cockroach and we're not sure that's a good idea just yet.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.28%. Comparing base (d385405) to head (bd7b958).
Report is 56 commits behind head on master.

Additional details and impacted files

Flag	Coverage Δ
activemq	?
cassandra	?
cockroachdb	93.19% <ø> (ø)
hive	?
hivemq	?
ignite	?
jboss_wildfly	?
kafka	?
presto	?
solr	?

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