use the same filtering process for every codec

[aler9]

this allows to apply features that were previously implemented for single codecs (like RTP packet resizing), to any codec, and simplifies future development.

[codecov]

Codecov Report

❌ Patch coverage is 50.70968% with 382 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.71%. Comparing base (c14fe77) to head (4f23c40).

Files with missing lines	Patch %	Lines
internal/stream/rtp_encoder.go	20.75%	164 Missing and 4 partials ⚠️
internal/stream/rtp_decoder.go	37.75%	98 Missing and 24 partials ⚠️
internal/stream/stream_format.go	59.49%	17 Missing and 15 partials ⚠️
internal/staticsources/rpicamera/source.go	0.00%	20 Missing ⚠️
internal/stream/unit_remuxer.go	86.00%	11 Missing and 3 partials ⚠️
internal/stream/stream.go	71.42%	4 Missing and 2 partials ⚠️
internal/test/static_source_parent.go	0.00%	6 Missing ⚠️
internal/protocols/rtsp/to_stream.go	0.00%	5 Missing ⚠️
internal/protocols/webrtc/to_stream.go	0.00%	5 Missing ⚠️
internal/recorder/format_fmp4.go	71.42%	2 Missing ⚠️
... and 1 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5324      +/-   ##
==========================================
+ Coverage   57.62%   57.71%   +0.09%     
==========================================
  Files         197      183      -14     
  Lines       15797    15358     -439     
==========================================
- Hits         9103     8864     -239     
+ Misses       5908     5712     -196     
+ Partials      786      782       -4     

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