Backwards compatible theta sketch aggregation

[davecromberge]

Servers running on versions before upgrading Pinot to the ThetaSketchAccumulator would return Sketches directly to the merge function. This ensures that there is backwards compatibility between the two.

This PR can be tagged with bugfix and addresses bug reported in #12042 (comment)

[codecov-commenter]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (17e1aa1) 61.62% compared to head (48ebe00) 61.58%.
Report is 3 commits behind head on master.

Files	Patch %	Lines
...n/DistinctCountThetaSketchAggregationFunction.java	37.50%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #12288      +/-   ##
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  Complexity     1153     1153              
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  Branches      20303    20310       +7     
============================================
- Hits          81020    80988      -32     
- Misses        44528    44599      +71     
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[jackjlli]

Thanks @davecromberge for the fast turnaround! Would you mind adding some thetha sketch queries in the pinot-compatibility-verifier test suite?

You can see some some queries in this file path in the repo:
compatibility-verifier/sample-test-suite/config/queries/feature-test-1-sql.queries
Thanks again for your contributions!

[davecromberge]

Hi @jackjlli thanks for pointing me to those tests. I've tried to replicate the problem using different commit refs in git history but it turns out that the merge function is not exercised in the compat checker. This is because only one server is started in the test suite.
Nevertheless, I've added the theta sketch aggregation to the queries and result tests for future coverage.

[jackjlli]

Thanks @davecromberge for fixing it! Here is the issue to track the work of testing with multiple brokers and servers in the compatibility test, so that such edge case can be easily captured: #12296