Emit per-query result-level caching metrics on Broker

[jtuglu1]

This is the first part of a 2-part PR set which aims to emit better metrics on per-query caching decisions (both result level and segment level).

If the result level cache on brokers is polled, a metric query/resultCache/hit is added which indicates whether the poll was a hit/miss. Dimensions are the normal query dimensions.

Description

It would be more ideal to add this as a dimension in the already-emitted query/time/query/bytes metrics, however these don't have a reliable way of passing context back up the call stack following Sequence creation.

Release note

Emit per-query result-level caching metrics on Broker

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Key changed/added classes in this PR

• MyFoo
• OurBar
• TheirBaz

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This PR has:

• [x] been self-reviewed.
  • [ ] using the concurrency checklist (Remove this item if the PR doesn't have any relation to concurrency.)
• [x] added documentation for new or modified features or behaviors.
• [ ] a release note entry in the PR description.
• [ ] added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• [ ] added or updated version, license, or notice information in licenses.yaml
• [ ] added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• [x] added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• [ ] added integration tests.
• [x] been tested in a test Druid cluster.