RUM-3741: Use BackpressureExecutor for SessionReplay event processing

[jonathanmos]

What does this PR do?

Uses the BackpressureExecutor for session replay event processing.

Motivation

The session replay event loop can experience backpressure, especially in applications with an endless feed.

Additional Notes

Anything else we should know when reviewing?

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

All modified and coverable lines are covered by tests ✅

Project coverage is 70.14%. Comparing base (eaa15cd) to head (9abafaf).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2116      +/-   ##
===========================================
- Coverage    70.23%   70.14%   -0.09%     
===========================================
  Files          721      721              
  Lines        26761    26756       -5     
  Branches      4484     4487       +3     
===========================================
- Hits         18794    18767      -27     
- Misses        6718     6745      +27     
+ Partials      1249     1244       -5     

Files	Coverage Δ
...nreplay/internal/recorder/SessionReplayRecorder.kt	96.75% <100.00%> (-0.13%)	⬇️

... and 23 files with indirect coverage changes