Fix real-time validation NPE when stream partition no longer available

[Jackie-Jiang]

When a stream partition is no longer available (reached end of life), trying to create a consuming segment for it can cause NPE.
This PR fixes the problem by not creating new consuming segment for partitions that have already reached end of life.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 60.52632% with 15 lines in your changes missing coverage. Please review.

Project coverage is 63.78%. Comparing base (59551e4) to head (1d3601d).
Report is 1289 commits behind head on master.

Files with missing lines	Patch %	Lines
.../core/realtime/PinotLLCRealtimeSegmentManager.java	60.52%	11 Missing and 4 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #14392      +/-   ##
============================================
+ Coverage     61.75%   63.78%   +2.02%     
- Complexity      207     1555    +1348     
============================================
  Files          2436     2660     +224     
  Lines        133233   145961   +12728     
  Branches      20636    22345    +1709     
============================================
+ Hits          82274    93096   +10822     
- Misses        44911    45989    +1078     
- Partials       6048     6876     +828     

Flag	Coverage Δ
custom-integration1	100.00% <ø> (+99.99%)	⬆️
integration	100.00% <ø> (+99.99%)	⬆️
integration1	100.00% <ø> (+99.99%)	⬆️
integration2	0.00% <ø> (ø)
java-11	63.74% <60.52%> (+2.03%)	⬆️
java-21	63.67% <60.52%> (+2.04%)	⬆️
skip-bytebuffers-false	63.77% <60.52%> (+2.03%)	⬆️
skip-bytebuffers-true	63.63% <60.52%> (+35.90%)	⬆️
temurin	63.78% <60.52%> (+2.02%)	⬆️
unittests	63.77% <60.52%> (+2.02%)	⬆️
unittests1	55.49% <ø> (+8.60%)	⬆️
unittests2	34.15% <60.52%> (+6.41%)	⬆️

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