[Backport 2.x] Enforcing append only setting for star-tree index (#17180)

[bharath-techie]

Description

Backport of #17180

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

✅ Gradle check result for b97a26c: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 71.93%. Comparing base (fcf5c35) to head (b97a26c).
Report is 2 commits behind head on 2.x.

Files with missing lines	Patch %	Lines
...java/org/opensearch/index/mapper/ObjectMapper.java	0.00%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##                2.x   #17184   +/-   ##
=========================================
  Coverage     71.93%   71.93%           
  Complexity    65937    65937           
=========================================
  Files          5341     5341           
  Lines        307108   307114    +6     
  Branches      44822    44824    +2     
=========================================
+ Hits         220928   220936    +8     
  Misses        67711    67711           
+ Partials      18469    18467    -2     

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