Retry processing of messages until no change between runs

[stefpiatek]

closes #393

• Allow env configuration of wait time for queues to empty before checking? Would be good to not wait during system tests

[codecov]

Codecov Report

Attention: Patch coverage is 88.60759% with 9 lines in your changes missing coverage. Please review.

Project coverage is 83.60%. Comparing base (de8ea69) to head (6e1b93a).

Files	Patch %	Lines
cli/src/pixl_cli/_message_processing.py	85.45%	8 Missing ⚠️
cli/src/pixl_cli/main.py	93.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #407      +/-   ##
==========================================
+ Coverage   83.04%   83.60%   +0.56%     
==========================================
  Files          76       81       +5     
  Lines        3061     3374     +313     
==========================================
+ Hits         2542     2821     +279     
- Misses        519      553      +34     

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[milanmlft]

Looks good to me, just a small suggestion/question regarding where --num-retries is/should be used.