browser (calls): conferences implementation: - Handle A/V conferences calls creation/joining by entering a conference room JID in the search box. - Group call box has been improved and is used both for group calls (small number of participants) and A/V conferences (larger number of participants). - Fullscreen button for group call is working. - Avatar/user nickname are shown in group call on peer user, as an overlay on video stream. - Use `user` metadata when present to display the right user avatar/name when receiving a stream from SFU (i.e. A/V conference). - Peer user have a new 3 dots menu with a `pin` item to (un)pin it (i.e. display it on full container with on top). - Updated webrtc to handle unidirectional streams correctly and to adapt to A/V conference specification. rel 448