Add some benchmarks for parsing and writing RTP packets

[ystreet]

No description provided.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 74.81%. Comparing base (5acf337) to head (94dea46).
Report is 3 commits behind head on main.

Files	Patch %	Lines
benches/write.rs	0.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #16      +/-   ##
==========================================
- Coverage   76.33%   74.81%   -1.53%     
==========================================
  Files           3        4       +1     
  Lines         393      401       +8     
==========================================
  Hits          300      300              
- Misses         93      101       +8     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.