Use multiple workers in MSQ WF drill test suite

[Akshat-Jain]

Description

Currently, MSQ WF drill test suite uses maxNumTasks: 2 (default).

This means we can't detect any issues/regressions via this test, when we use multiple workers.

This PR updates the MSQ WF drill test suite to use maxNumTasks: 5.

However, there are some test cases which can give different correct results across different runs due to MixShuffleSpec being present in the previous stage. Such test cases have been overridden to use a single worker. This has been done for 8 tests.

Some tests have been modified to give deterministic result, while ensuring that the test is still validating what it was originally added for.

I've ran MSQDrillWindowQueryTest 20+ times locally to ensure no flakiness for any other test that's not overridden to use a single worker.

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This PR has:

• been self-reviewed.
• 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.

[cryptoe]

Failures seems unrelated to this PR.