[Backport 2.x] [Star tree] Star tree file formats refactoring and fixing offset bug

[opensearch-trigger-bot]

Backport 80ff07e from #15975.

[github-actions]

✅ Gradle check result for 732aa12: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 77.04918% with 14 lines in your changes missing coverage. Please review.

Project coverage is 71.66%. Comparing base (bfdc30c) to head (732aa12).
Report is 4 commits behind head on 2.x.

Files with missing lines	Patch %	Lines
...be/startree/utils/SequentialDocValuesIterator.java	68.75%	2 Missing and 3 partials ⚠️
...cube/startree/builder/StarTreeDocsFileManager.java	50.00%	1 Missing and 2 partials ⚠️
...eindex/datacube/startree/index/StarTreeValues.java	76.92%	1 Missing and 2 partials ⚠️
...tartree/utils/iterator/StarTreeValuesIterator.java	57.14%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x   #15991      +/-   ##
============================================
- Coverage     71.67%   71.66%   -0.02%     
- Complexity    64624    64627       +3     
============================================
  Files          5276     5278       +2     
  Lines        302298   302295       -3     
  Branches      43992    43990       -2     
============================================
- Hits         216674   216640      -34     
- Misses        67532    67599      +67     
+ Partials      18092    18056      -36     

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