Fix document creation process for testCacheFilesAreClosedAfterUse IT

[kotwanikunal]

Description

• Uses the standard methods defined within SearchableSnapshotIT to perform index creation, doc creation and green checks for testCacheFilesAreClosedAfterUse
• Current implementation led to incorrect green checks because of missing shard and replica configs

Issues Resolved

• Resolves [BUG] org.opensearch.snapshots.SearchableSnapshotIT.testCacheFilesAreClosedAfterUse is flaky #6686

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)

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[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/12801/
• CommitID: 15bf4f4

[codecov-commenter]

Codecov Report

Merging #6797 (15bf4f4) into main (f40fa82) will decrease coverage by 0.04%.
The diff coverage is n/a.

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@@             Coverage Diff              @@
##               main    #6797      +/-   ##
============================================
- Coverage     70.75%   70.72%   -0.04%     
+ Complexity    59230    59164      -66     
============================================
  Files          4810     4810              
  Lines        283487   283487              
  Branches      40877    40877              
============================================
- Hits         200577   200485      -92     
- Misses        66408    66519     +111     
+ Partials      16502    16483      -19     

see 502 files with indirect coverage changes

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[tlfeng]

Thank you for fixing the flaky test!