Record skipped files in prometheus

[stephen-riggs]

Will allow us to be notified when files are skipped due to visit end times

[codecov]

Codecov Report

❌ Patch coverage is 37.50000% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 33.56%. Comparing base (41e0dfa) to head (a4c3c46).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #642      +/-   ##
==========================================
+ Coverage   33.52%   33.56%   +0.03%     
==========================================
  Files          92       92              
  Lines       11245    11254       +9     
  Branches     1474     1474              
==========================================
+ Hits         3770     3777       +7     
- Misses       7348     7350       +2     
  Partials      127      127              

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[tieneupin]

Your PR works. It not working in the dev setup is a fault of mine when configuring the routing logic that I've now addressed.

I've optimised the logic so that the skipped files are tracked on a per rsyncer basis, and have also added logic to reset the counter when a flush is successfully triggered.

[stephen-riggs]

Thanks for looking, and for adding the logic to set the skipped files values to zero when started and flushed.

I had intentionally not included the rsyncer in the tracking, as I think we only care about skipped files on a session level, but no harm in adding the rsyncer anyway.