[Draft] track the use of partition upsert metadata mgr to reset preloading flag

[klsince]

Try to use refCnt to track threads using partition upsert metadata mgr so that we can be sure when we can reset the isPreloading flag, so that the mgr can load segments via preloading again, e.g. when the table partition is rebalanced back to the old server.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 28.00000% with 18 lines in your changes are missing coverage. Please review.

Project coverage is 62.22%. Comparing base (59551e4) to head (19e7268).
Report is 310 commits behind head on master.

Files	Patch %	Lines
...ata/manager/realtime/RealtimeTableDataManager.java	0.00%	7 Missing ⚠️
...cal/upsert/BasePartitionUpsertMetadataManager.java	30.00%	7 Missing ⚠️
...a/manager/realtime/RealtimeSegmentDataManager.java	0.00%	1 Missing and 1 partial ⚠️
...psert/ConcurrentMapTableUpsertMetadataManager.java	66.66%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #12938      +/-   ##
============================================
+ Coverage     61.75%   62.22%   +0.47%     
+ Complexity      207      198       -9     
============================================
  Files          2436     2503      +67     
  Lines        133233   136498    +3265     
  Branches      20636    21119     +483     
============================================
+ Hits          82274    84932    +2658     
- Misses        44911    45279     +368     
- Partials       6048     6287     +239     

Flag	Coverage Δ
custom-integration1	<0.01% <0.00%> (-0.01%)	⬇️
integration	<0.01% <0.00%> (-0.01%)	⬇️
integration1	<0.01% <0.00%> (-0.01%)	⬇️
integration2	0.00% <0.00%> (ø)
java-11	62.16% <28.00%> (+0.45%)	⬆️
java-21	62.10% <28.00%> (+0.47%)	⬆️
skip-bytebuffers-false	62.18% <28.00%> (+0.43%)	⬆️
skip-bytebuffers-true	62.07% <28.00%> (+34.34%)	⬆️
temurin	62.22% <28.00%> (+0.47%)	⬆️
unittests	62.21% <28.00%> (+0.47%)	⬆️
unittests1	46.68% <0.00%> (-0.21%)	⬇️
unittests2	28.01% <28.00%> (+0.28%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.