Fetch active tasks from memory in SeekableStreamSupervisor

[AmatyaAvadhanula]

The SeekableStreamSupervisor fetches the task payloads for every active task in its datasource twice every RunNotice.
In large clusters, this may cause the RunNotice to take a long time when it may be able to complete within a couple of seconds otherwise.
If there are hundreds of supervisors, there are 4 * supervisors calls to the metadata store every minute to fetch all the active datasource task payloads. This change can help reduce the load on the db significantly in such cases.

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.
• 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.
• 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.

[abhishekagarwal87]

What problems does this PR address?

[AmatyaAvadhanula]

The SeekableStreamSupervisor fetches the task payloads for every active task in its datasource twice every RunNotice.
In large clusters, this may cause the RunNotice to take a long time when it may be able to complete within a couple of seconds otherwise.
If there are hundreds of supervisors, there are 4 * supervisors calls to the metadata store every minute to fetch all the active datasource task payloads. This change can help reduce the load on the db significantly in such cases.

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[kfaraz]

@AmatyaAvadhanula , the change here makes sense to me.
Can we move this move this from Draft to Ready?
There seem to be some merge conflicts.

[kfaraz]

LGTM 🚀

@AmatyaAvadhanula , the SeekableStreamSupervisor also makes calls to taskStorage.getTask(). I wonder if these calls should also first check for those tasks in memory. If yes, then we should probably just remove TaskStorage from SeekableStreamSupervisor and use TaskQueryTool instead and route everything from there.

The TaskQueryTool can decide if a task should be served from memory or storage.
What do you think?