[Backport 2.x] Optimise snapshot deletion to speed up snapshot deletion and creation(#15568)

[ashking94]

Backport 3fc0139 from #15568

[github-actions]

❌ Gradle check result for cd548cd: FAILURE

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 cd548cd: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 82.14286% with 10 lines in your changes missing coverage. Please review.

Project coverage is 71.71%. Comparing base (017f7d4) to head (cd548cd).
Report is 8 commits behind head on 2.x.

Files with missing lines	Patch %	Lines
...ch/repositories/blobstore/BlobStoreRepository.java	80.76%	10 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x   #15724      +/-   ##
============================================
- Coverage     71.72%   71.71%   -0.01%     
- Complexity    64329    64391      +62     
============================================
  Files          5261     5262       +1     
  Lines        300936   301051     +115     
  Branches      43822    43833      +11     
============================================
+ Hits         215854   215911      +57     
- Misses        67024    67115      +91     
+ Partials      18058    18025      -33     

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