refactor: use sleap-io built-in video matching methods

[jaw039]

Summary

Replaced custom video matching logic in sleap_nn/evaluation.py with sleap-io's built-in matching methods.

Changes

• Removed old manual frame/video matching logic
• Added sleap-io built-in matching functions

Issue

#368

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.83%. Comparing base (ff91433) to head (e381892).
⚠️ Report is 69 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #380      +/-   ##
==========================================
- Coverage   95.28%   93.83%   -1.46%     
==========================================
  Files          49       49              
  Lines        6765     7183     +418     
==========================================
+ Hits         6446     6740     +294     
- Misses        319      443     +124     

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