[WIP] Add configurable audio device ID for WebRTC on Android

[jonathanphilippou]

Overview

This PR adds the ability to configure the audio device ID used by WebRTC on Android. Currently, the WebRTC implementation on React Native only reports a single hardcoded "audio-1" device regardless of what physical microphone is connected, making it difficult to work with multiple audio inputs or integrate with other audio libraries like Expo AV.

Changes

• Added a configurable defaultAudioDeviceId field to WebRTCModuleOptions
• Modified GetUserMediaImpl to use this configurable ID throughout the audio device lifecycle
• Added support for overriding the default via audio constraints in getUserMedia
• Added new JavaScript APIs to get and set the default audio device ID
• Updated all related code to use the configurable device ID instead of hardcoded "audio-1"

JavaScript API

// Set the default audio device ID
setDefaultAudioDeviceId('expo-av-audio');

// Get the current default audio device ID
const deviceId = await getDefaultAudioDeviceId();

Use Cases

This PR helps solve several issues:

1. Integration with other audio libraries: Allows setting the audio device ID to match what Expo AV or other libraries use
2. External microphone support: Makes it easier to handle external microphones that may not be detected correctly with the default ID
3. Cross-platform consistency: Better audio device handling across platforms

Testing

I've tested this with both built-in and external microphones on Android. The configurable ID effectively allows WebRTC to use the same microphone as other audio APIs by setting the appropriate device ID.

Related Issues

This addresses the common issue where WebRTC and other audio APIs (like Expo AV) can't use the same microphone device on Android.

[jonathanphilippou]

I'll undo all of the reformatting changes from my editor. sorry about that 😅

[jonathanphilippou]

i will delete this kind of thing after i know what i have works

[jonathanphilippou]

i will delete this when i know my code works. sorry about that

[davidliu]

1. I don't see how this actually affects any of the audio routing. As far as I can tell, the code just saves an audioDeviceId, but doesn't actually use it for anything.
2. If you'd like to make this change, open a PR on the upstream repo instead. This repo is for LiveKit specific changes that aren't applicable more broadly.