[feature] Android: USB Sound Card Support

[kNoAPP]

Is your feature request related to a problem? Please describe. I'm trying to use an external microphone with LiveKit's example app on Android. I have plugged in a USB-C microphone to my Pixel phone's port. On the example Flutter LiveKit app, there's no way to select this device. The microphone list does not show this new device. Yet on my Pixel's recorder app, I can access the USB-C microphone just fine. The recorder app perfectly transcribes audio coming off my USB-C microphone (tested via direct line from PC audio-out to USB-C mic in). I can even switch back to the regular microphone while the USB-C one is plugged in.

Describe the solution you'd like

When a USB sound card is plugged into an Android device, an additional "External Microphone" option should be present in the available audio device list. An AudioTrack provisioned from the device id should then pull sound from the USB sound card.

Describe alternatives you've considered

None

Additional context

Issue originates from LiveKit Community Slack: https://livekit-users.slack.com/archives/C07FVFGAUKX/p1726270632273329