Permissively parse SDPs unless completely invalid

[philipch07]

Description

Instead of throwing errors since there are numerous SDP types, we can be more permissive by allowing them to be ignored (with a logged warning) and instead bubble up the last error if they all failed.

This is a re-implementation of pion/sdp#233, but in a more appropriate place (see pion/sdp#233 (comment)).

Reference issue

Resolves #1315.

[codecov]

Codecov Report

❌ Patch coverage is 69.56522% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.26%. Comparing base (8d685da) to head (71e1084).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
sdp.go	69.56%	5 Missing and 2 partials ⚠️

❌ Your patch status has failed because the patch coverage (69.56%) 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    #3297      +/-   ##
==========================================
- Coverage   84.30%   84.26%   -0.05%     
==========================================
  Files          80       80              
  Lines        9133     9144      +11     
==========================================
+ Hits         7700     7705       +5     
- Misses       1014     1019       +5     
- Partials      419      420       +1     

Flag	Coverage Δ
go	84.26% <69.56%> (-0.05%)	⬇️

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[JoTurk]

Pretty cool change, and I like the early return.