Include sdpMid and sdpMLineIndex for ICECandidates returned by OneICECandidate

[joeturki]

Description

Currently, Pion returns an empty sdpMid and a 0 sdpMLineIndex. This PR ensures Pion returns the corresponding sdpMid and sdpMLineIndex for ICE candidates for clients that expects it. Fixes trickle issues.

Changes

1. ICECandidates: New fields SDPMid and SDPMLineIndex.
2. ICECandidates: Two new constructors newIdentifiedICECandidateFromICE and newIdentifiedICECandidatesFromICE.
3. ICEGatherer: SetMediaStreamIdentification and return the correct SDPMid and SDPMLineIndex.
4. extractICEDetails: Return a struct instead of multiple values sdpICEDetails, return the picked SDPMid and SDPMLineIndex.
5. Added new tests.

Reference issue

Fixes #2690
Fixes #1833

[codecov]

Codecov Report

Attention: Patch coverage is 87.17949% with 10 lines in your changes missing coverage. Please review.

Project coverage is 78.00%. Comparing base (1ee0299) to head (aa6f53c).

Files with missing lines	Patch %	Lines
icecandidate.go	71.42%	4 Missing and 2 partials ⚠️
peerconnection.go	75.00%	0 Missing and 2 partials ⚠️
sdp.go	93.10%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2990      +/-   ##
==========================================
+ Coverage   77.93%   78.00%   +0.06%     
==========================================
  Files          89       89              
  Lines       10546    10587      +41     
==========================================
+ Hits         8219     8258      +39     
  Misses       1838     1838              
- Partials      489      491       +2     

Flag	Coverage Δ
go	79.57% <87.17%> (+0.06%)	⬆️
wasm	63.51% <71.42%> (+<0.01%)	⬆️

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[Sean-Der]

@joeturki This is the highest quality PR I have seen in a long time. This is really impressive stuff.

When I read this I feel like I am reading code of someone who has been intimately involved with WebRTC/Go for years. I am so excited for you to be more involved :)

[Sean-Der]

Mind squashing everything into one commit and address the comments I left! Then we can merge this right away :)

[joeturki]

Thanks :) I think it's ready.