add a new query laning metrics to visualize lane assignment

[isandeep41]

This PR aims to introduce a new metrics query/priority which will help to visualize the assigned lane if the Laning Strategy is enabled.

The Grafana Dashboard shows the distribution of high/low lanes on a Druid cluster running Druid version 0.22.1

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This PR has:

• been self-reviewed.
  • using the concurrency checklist (Remove this item if the PR doesn't have any relation to concurrency.)
• added documentation for new or modified features or behaviors.
• 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.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• added integration tests.
• been tested in a test Druid cluster.

[asdf2014]

👍 Overall LGTM, thanks for your contirubtion, also I leave a few small suggestions

[jihoonson]

@isandeep41 @FrankChen021 @asdf2014, thank you for getting this PR merged. It seems that Travis has started to fail after this PR is merged (https://app.travis-ci.com/github/apache/druid/builds/247395466). Can you please check the Travis failure? This is a blocker issue since the CI is broken.

[gianm]

I included a fix in #12307. It was a logical conflict between this patch and #12202, that as far as I can tell only affected the test case QueryableModuleTest.

[jihoonson]

Thank you @gianm!

[FrankChen021]

Thank you @gianm

[isandeep41]

Thanks @gianm