[Backport 2.x] Optimize innerhits query performance

[opensearch-trigger-bot]

Backport 92088be from #16937.

[github-actions]

❌ Gradle check result for d67b79b: TIMEOUT

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

✅ Gradle check result for d67b79b: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 4.34783% with 22 lines in your changes missing coverage. Please review.

Project coverage is 71.90%. Comparing base (bd885f7) to head (d67b79b).
Report is 4 commits behind head on 2.x.

Files with missing lines	Patch %	Lines
...va/org/opensearch/index/mapper/DocumentMapper.java	0.00%	15 Missing ⚠️
...n/java/org/opensearch/search/fetch/FetchPhase.java	0.00%	6 Missing ⚠️
...org/opensearch/index/query/NestedQueryBuilder.java	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x   #17084      +/-   ##
============================================
+ Coverage     71.84%   71.90%   +0.05%     
- Complexity    65595    65625      +30     
============================================
  Files          5318     5318              
  Lines        305846   305851       +5     
  Branches      44602    44603       +1     
============================================
+ Hits         219739   219911     +172     
+ Misses        67752    67631     -121     
+ Partials      18355    18309      -46     

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