[BugFix] Serialize TlsSpec when executing DataIngestion backfill job

[hongkunxu]

Fixes a NotSerializableException caused by TlsSpec not implementing Serializable.
Added implements Serializable to TlsSpec to allow objects containing it to be serialized properly during DataIngestion Backfill job execution.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 63.31%. Comparing base (1a476de) to head (df8865f).
Report is 471 commits behind head on master.

Files with missing lines	Patch %	Lines
...apache/pinot/spi/ingestion/batch/spec/TlsSpec.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #16381      +/-   ##
============================================
+ Coverage     62.90%   63.31%   +0.41%     
+ Complexity     1386     1363      -23     
============================================
  Files          2867     2976     +109     
  Lines        163354   172777    +9423     
  Branches      24952    26459    +1507     
============================================
+ Hits         102755   109402    +6647     
- Misses        52847    55029    +2182     
- Partials       7752     8346     +594     

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-11	63.27% <0.00%> (+0.40%)	⬆️
java-21	63.29% <0.00%> (+0.47%)	⬆️
skip-bytebuffers-false	?
skip-bytebuffers-true	?
temurin	63.31% <0.00%> (+0.41%)	⬆️
unittests	63.31% <0.00%> (+0.41%)	⬆️
unittests1	56.44% <0.00%> (+0.62%)	⬆️
unittests2	33.31% <0.00%> (-0.26%)	⬇️

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