Add NAF Phoenix Adapter

[johnshaughnessy]

This PR changes a few things.

• There is a new NAF adapter called PhoenixAdapter. The PhoenixAdapter handles naf and nafr events on the hub:${hubId} phoenix channel, and tells NAF when participants join and leave the hub room. (It uses Presence to know about the other participants.)
• The DialogAdapter does not have to care about NAF anymore, so it doesn't. We give dialog only the information it needs (serverParams, hubId, turn info etc) to join the protoo room and establish WebRTC connections with the help of mediasoup.
• Mic state is simpler:
  • The source of truth is APP.dialog.isMicEnabled.
  • The mic state is not stored in localStorage or in a muted css class on the scene.
  • We do not toggle the microphone when selecting a new input device from the preference menu.
• Hub channel presence events are handled by various event handlers, rather than having a small number of event handlers do a bunch of work.

Built on top of #4364