Test cases for RTCRtpParameters.codecs.
Includes some tests that compat mode ignores any attempt to set .codecs.
Also includes some miscellaneous wpt fixes and meta file updates.
Differential Revision: https://phabricator.services.mozilla.com/D209304
bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1534687
gecko-commit: 42c06449d631dd62a20e2e2b7213836bf4493317
gecko-reviewers: jib