use jspecify annotations

[sullis]

Context

https://jspecify.dev/docs/start-here/

https://jspecify.dev/docs/user-guide/

https://jspecify.dev/blog/release-1.0.0/

https://www.infoq.com/news/2024/08/jspecify-java-nullability/

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 57.14286% with 3 lines in your changes missing coverage. Please review.

Project coverage is 61.93%. Comparing base (59551e4) to head (9f29e87). Report is 1176 commits behind head on master.

Files with missing lines	Patch %	Lines
...ain/java/org/apache/pinot/common/data/Segment.java	0.00%	1 Missing :warning:
...ta/segment/SegmentZKMetadataCustomMapModifier.java	0.00%	1 Missing :warning:
...pinot/controller/util/TableRetentionValidator.java	0.00%	1 Missing :warning:

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #13822      +/-   ##
============================================
+ Coverage     61.75%   61.93%   +0.18%     
+ Complexity      207      198       -9     
============================================
  Files          2436     2558     +122     
  Lines        133233   141224    +7991     
  Branches      20636    21977    +1341     
============================================
+ Hits          82274    87471    +5197     
- Misses        44911    47089    +2178     
- Partials       6048     6664     +616     

Flag	Coverage Δ
custom-integration1	<0.01% <0.00%> (-0.01%)	:arrow_down:
integration	<0.01% <0.00%> (-0.01%)	:arrow_down:
integration1	<0.01% <0.00%> (-0.01%)	:arrow_down:
integration2	0.00% <0.00%> (ø)
java-11	61.90% <57.14%> (+0.19%)	:arrow_up:
java-21	61.80% <57.14%> (+0.18%)	:arrow_up:
skip-bytebuffers-false	61.92% <57.14%> (+0.18%)	:arrow_up:
skip-bytebuffers-true	61.78% <57.14%> (+34.05%)	:arrow_up:
temurin	61.93% <57.14%> (+0.18%)	:arrow_up:
unittests	61.93% <57.14%> (+0.18%)	:arrow_up:
unittests1	46.37% <66.66%> (-0.52%)	:arrow_down:
unittests2	27.80% <0.00%> (+0.07%)	:arrow_up:

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