Share Kinesis ingestion fixture and restore CI coverage

[xiangfu0]

Summary

• add an explicit serial TestNG suite for the nested Kinesis ingestion tests, which are not selected by the current top-level alphabetical includes
• share one Pinot and LocalStack fixture across RealtimeKinesisIntegrationTest and KinesisShardChangeTest while keeping per-class tables, schemas, and streams isolated
• make setup, publisher-thread handling, and teardown failure-safe so one scenario cannot leak state into the next
• run the suite on existing test Set 2 before coverage upload; the workflow still has exactly two matrix jobs

Validation

• full Docker-backed suite: 23 tests, 0 failures, 0 errors, 0 skips; TestSuite 900.2s, Maven 15:09
• pinot-integration-tests test-compile passed
• Spotless, Checkstyle, license format/check, and git diff check passed
• TestNG XML, shell script, workflow YAML, and effective-POM profile resolution passed
• independent lifecycle and isolation review found no remaining blocker

Runtime note

This draft intentionally restores missing CI coverage, so it adds work even after fixture sharing. The local run took about 15 minutes. Hosted CI should establish the actual Set 2 cost and whether a narrower smoke matrix is preferable before marking the PR ready.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.62%. Comparing base (baaf0a7) to head (28bf1b1).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #19196      +/-   ##
============================================
- Coverage     66.62%   66.62%   -0.01%     
  Complexity     1423     1423              
============================================
  Files          3443     3443              
  Lines        218626   218626              
  Branches      34792    34792              
============================================
- Hits         145662   145661       -1     
- Misses        61240    61245       +5     
+ Partials      11724    11720       -4     

Flag	Coverage Δ
custom-integration1	100.00% <ø> (ø)
integration	100.00% <ø> (ø)
integration1	100.00% <ø> (ø)
integration2	0.00% <ø> (ø)
java-25	66.62% <ø> (-0.01%)	⬇️
temurin	66.62% <ø> (-0.01%)	⬇️
unittests	66.62% <ø> (-0.01%)	⬇️
unittests1	57.19% <ø> (-0.01%)	⬇️
unittests2	38.90% <ø> (+<0.01%)	⬆️

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[xiangfu0]

Folded into #19190.