Lobby Improvements

[ptrbrynt]

The StreamLobbyView and StreamLobbyVideo components seem limited in a couple of important ways, in order of priority in my opinion:

1. They always use StreamVideo.instance, which causes problems for apps which initialize Stream in another way (e.g. StreamVideo.create)
2. They do not include audio level or network quality indicators

Suggested Improvements

1. Allow us to pass in an instance of StreamVideo, and only fall back on StreamVideo.instance if another instance is not provided
2. Add audio/network indicators to the video preview