Improve unit test coverage for MSQ

[LakshSingla]

Description

This PR adds a new set of tests called MSQFaultsTest that aims to improve the testing coverage for MSQ by adding new unit tests for when the query should fault.

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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.
• 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.

[adarshsanjeev]

Thanks for the PR!
Tests added look good to me. Should there also be tests for TooManyInputFilesFault etc here?

[adarshsanjeev]

New test case looks good as well. Thanks for making the changes!

[kfaraz]

@LakshSingla , it seems a real overkill to have 30k rows of data just to get a specific exception in a unit test.
Can we simplify this somehow?

[LakshSingla]

@kfaraz MAX_PARTITIONS (25k) is a constant defined above which the query would fail. To get this many partitions, in my understanding we would require at least 25000 rows. I can think of the following options to prevent this static file here:

1. Create a file programmatically and then run the tests.
2. Create a method and override MAX_WORKERS (which doesn't seem right to me to do for the sake of testing).
3. Use some Guice magic to inject MAX_WORKERS (similar reasoning as above).
   Do you have any opinions on the above or an alternate approach that you think might be suitable? Thanks!

[kfaraz]

Yes, @LakshSingla , the first option seems most reasonable. You shouldn't have to generate the file either. You could maybe add a utility method in MsqTestBase which gives you a mock file with the required number of rows and columns?

[cryptoe]

I think we can add a new class for this and the previous method. MSQTestFileUtils?

[cryptoe]

Thanks @LakshSingla !!