PoC 2-way audio on iOS WebRTC player

### Description

- Add 2-way audio to the existent webrtc player, creating a channel to send microphone data back to core

### Additional context

- Requires changes in core

Start by locating the existing WebRTC player in the iOS project and tracing how it communicates with core. Review the core changes required for a return audio channel, then verify that microphone data can travel from the iOS player back to core while the existing player behavior remains intact.

Written by the indexing model from the issue text.