Adding codecs to the RtpParameters returned by an RtpSender.

Contains every field except for sdpFmtpLine.
Setting a reordered list of codecs is not yet supported.

R=glaznev@webrtc.org, pthatcher@webrtc.org, skvlad@webrtc.org, tkchin@webrtc.org

Review URL: https://codereview.webrtc.org/1885473004 .

Cr-Original-Commit-Position: refs/heads/master@{#12453}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 0cd086b70ec939cad25768d5e17a61da23613281
18 files changed