Channel logging improvements

[joostjager]

Additional trace logs that helped with debugging #4218 and might be generally useful.

[ldk-reviews-bot]

I've assigned @jkczyz as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.32%. Comparing base (bb5504e) to head (0647af3).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4242      +/-   ##
==========================================
- Coverage   89.33%   89.32%   -0.02%     
==========================================
  Files         180      180              
  Lines      138680   138683       +3     
  Branches   138680   138683       +3     
==========================================
- Hits       123888   123876      -12     
- Misses      12172    12182      +10     
- Partials     2620     2625       +5     

Flag	Coverage Δ
fuzzing	35.00% <14.28%> (-0.99%)	⬇️
tests	88.68% <100.00%> (-0.01%)	⬇️

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