ai/live: Add a desync query parameter to WHEP.

[j0sh]

This gives audio and video tracks a separate mid which stops the browser from trying to keep playback in sync. This may lead to desynced audio and video but improves latency.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 31.51820%. Comparing base (aca2275) to head (84d028d).

Files with missing lines	Patch %	Lines
media/whep_server.go	0.00000%	11 Missing ⚠️

Additional details and impacted files

@@                 Coverage Diff                 @@
##              master       #3783         +/-   ##
===================================================
- Coverage   31.52544%   31.51820%   -0.00724%     
===================================================
  Files            159         159                 
  Lines          47901       47912         +11     
===================================================
  Hits           15101       15101                 
- Misses         31911       31922         +11     
  Partials         889         889                 

Files with missing lines	Coverage Δ
media/whep_server.go	0.00000% <0.00000%> (ø)

... and 2 files with indirect coverage changes

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Files with missing lines	Coverage Δ
media/whep_server.go	0.00000% <0.00000%> (ø)

... and 2 files with indirect coverage changes

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