RUM-6171 use FileObserver to limit calls to filesystem

[0xnm]

What does this PR do?

The same as #2718, just branch moved directly to the repo.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 66.66667% with 5 lines in your changes missing coverage. Please review.

Project coverage is 69.81%. Comparing base (dc4ab79) to head (ecb5cc6).
Report is 19 commits behind head on develop.

Files with missing lines	Patch %	Lines
...al/persistence/file/batch/BatchFileOrchestrator.kt	66.67%	2 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2720      +/-   ##
===========================================
- Coverage    69.85%   69.81%   -0.04%     
===========================================
  Files          823      823              
  Lines        30626    30635       +9     
  Branches      5157     5159       +2     
===========================================
- Hits         21391    21385       -6     
- Misses        7785     7808      +23     
+ Partials      1450     1442       -8     

Files with missing lines	Coverage Δ
...al/persistence/file/batch/BatchFileOrchestrator.kt	91.67% <66.67%> (-3.30%)	⬇️

... and 35 files with indirect coverage changes

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