Add interceptor to aggregate CCFB reports

[mengelbart]

Alternative but cleaner implementation for congestion control feedback receiver (#300). The main difference between this and #300 is that #300 organizes the feedback per stream, while this version organizes it as a single linear stream, which is easier to process. If one still needs to know which stream a packet was sent on, that information is still included in the reports for each packet.

[codecov]

Codecov Report

❌ Patch coverage is 78.77095% with 76 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.74%. Comparing base (8492094) to head (ceaeb98).

Files with missing lines	Patch %	Lines
pkg/rtpfb/interceptor.go	75.51%	30 Missing and 6 partials ⚠️
pkg/rtpfb/twcc_receiver.go	70.42%	21 Missing ⚠️
pkg/rtpfb/history.go	79.78%	14 Missing and 5 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #374      +/-   ##
==========================================
+ Coverage   78.62%   78.74%   +0.11%     
==========================================
  Files          82       86       +4     
  Lines        5109     5467     +358     
==========================================
+ Hits         4017     4305     +288     
- Misses        921      982      +61     
- Partials      171      180       +9     

Flag	Coverage Δ
go	78.74% <78.77%> (+0.11%)	⬆️

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