Fix num_reports usage, see errata 8166

[mengelbart]

There was an errata about the usage of num_reports, and if I understand it correctly, Pion uses the now outdated interpretation of num_reports. This PR fixes this. I don't know if this will break users. Probably only when they try to interop with clients using the old interpretation (like old versions of Pion).

The errata can be found here:
https://www.rfc-editor.org/errata/eid8166

and the corresponding discussions on the mailing list:
https://mailarchive.ietf.org/arch/msg/avt/jCjC3nk52iW0_NHx64bSx8_nn_E/

The overflowEndSequence test case looks wrong to me. It shouldn't error, but instead, wrap the sequence number around. I added a corresponding test case for that. Seems like a bug in the old implementation?

[mengelbart]

Looks like we ran into this before...
a6ba630

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 77.70%. Comparing base (ec84594) to head (ace5356).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
rfc8888.go	66.66%	0 Missing and 1 partial ⚠️

❌ Your patch status has failed because the patch coverage (66.66%) is below the target coverage (70.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #187      +/-   ##
==========================================
- Coverage   77.86%   77.70%   -0.17%     
==========================================
  Files          22       22              
  Lines        2553     2548       -5     
==========================================
- Hits         1988     1980       -8     
- Misses        470      472       +2     
- Partials       95       96       +1     

Flag	Coverage Δ
go	77.70% <66.66%> (-0.17%)	⬇️
wasm	77.70% <66.66%> (-0.17%)	⬇️

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[aalekseevx]

The new behavior definitely makes more sense.

[Sean-Der]

LGTM! @mengelbart

You don't need to wait for me in the future. I am totally ok with you merging things without me. @aalekseevx knows RTP/RTCP better then me these days :)