Add method createSegmentMessageHandlerFactory in BaseServerStarter

[J-HowHuang]

Description

For any children class inheriting BaseServerStarter, this change allows it to override the method to provide customized message handler factory

Changes

1. Add a new method createSegmentMessageHandlerFactory in BaseServerStarter to provide SegmentMessageHandlerFactory and register.
2. Change the private variables in SegmentMessageHandlerFactory to protected

[Jackie-Jiang]

Let's also allow creating custom StateModelFactory to make all Helix related handler pluggable

[J-HowHuang]

@Jackie-Jiang Do you want that to be in the same PR?

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.60%. Comparing base (78e38eb) to head (e4cf14b).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
.../pinot/server/starter/helix/BaseServerStarter.java	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #18298      +/-   ##
============================================
+ Coverage     63.58%   63.60%   +0.02%     
  Complexity     1659     1659              
============================================
  Files          3245     3247       +2     
  Lines        197441   197482      +41     
  Branches      30564    30566       +2     
============================================
+ Hits         125536   125614      +78     
+ Misses        61856    61816      -40     
- Partials      10049    10052       +3     

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	63.58% <0.00%> (+8.07%)	⬆️
java-21	63.57% <0.00%> (+<0.01%)	⬆️
temurin	63.60% <0.00%> (+0.02%)	⬆️
unittests	63.60% <0.00%> (+0.02%)	⬆️
unittests1	55.55% <ø> (+<0.01%)	⬆️
unittests2	35.07% <0.00%> (+0.03%)	⬆️

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