Add support to dynamically resize threadpools size (#16236)

[gbbafna]

Backport 35c366d from #16269

[github-actions]

✅ Gradle check result for c2d8bcf: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 53.44828% with 27 lines in your changes missing coverage. Please review.

Project coverage is 71.82%. Comparing base (5947002) to head (c2d8bcf).
Report is 15 commits behind head on 2.x.

Files with missing lines	Patch %	Lines
...ain/java/org/opensearch/threadpool/ThreadPool.java	52.63%	25 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x   #16330      +/-   ##
============================================
+ Coverage     71.74%   71.82%   +0.08%     
- Complexity    65022    65116      +94     
============================================
  Files          5302     5305       +3     
  Lines        303866   304040     +174     
  Branches      44192    44221      +29     
============================================
+ Hits         218012   218382     +370     
+ Misses        67648    67485     -163     
+ Partials      18206    18173      -33     

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