[WebAPI] Update RTCIceCandidate member attribute and parsing

[dipikabh]

Acceptance criteria

• The listed features are documented sufficiently on MDN
• BCD is updated
• Interactive example and data repos are updated if appropriate
• The content has been reviewed as needed

For folks helping with Firefox related documentation

• Set bugs to dev-doc-complete
• Add entry to Firefox release notes for enabled/preview features
• Add/remove entry to Firefox experimental features page for preference/released features

Related Gecko bugs

Bug 1322186: Make RTCIceCandidate members readonly and add members parsed from candidate string

Other

• Check content open issues to see if any pertain to the subject matter. If there are any that can be closed because of the work, do so. If there are any that can be fixed relatively quickly because of the knowledge from completing this issue and you have time, feel free to go ahead and fix them.

[hamishwillee]

FF126 updates RTCIceCandidate to match spec, with the exception of two missing properties: relayProtocol, url (will be added by https://bugzilla.mozilla.org/show_bug.cgi?id=1886013).

Changes:

• Existing properties now read-only: candidate, sdpMid, sdpMLineIndex, usernameFragment

• The toJSON() method now returns an object that matches the format of the object passed to the RTCIceCandidate constructor (a RTCIceCandidateInit according to spec)

• New properties: foundation, component, priority, address, protocol, port, type, tcpType, relatedAddress, relatedPort
  Support matches what I see in https://mdn-bcd-collector.gooborg.com/tests/api/RTCIceCandidate

Might also be updates to RTCIceCandidatePairStats but no indications things have changed:

• Nothing useful coming out of https://mdn-bcd-collector.gooborg.com/tests/api/RTCStatsReport/type_candidate-pair
• https://wpt.live/webrtc-stats/supported-stats.https.html same results

All of this seems to match the documentation, so work is BCD, Release note.

[hamishwillee]

Status

• BCD - Updates for Firefox 126 beta browser-compat-data#22854
  • Several updates for read-only and adding bug links where useful
• Docs - none required as far as I can tell.
• Release note FF126 Relnote: RTCIceCandidate support #33110
• dev-docs-complete