core: support audio streaming

### Current behaviour

When connecting a microphone there's no option in BlueOS to stream the audio to the surface, or record it.

### Expected or desired behaviour

Companion [supported automatic streaming of the BR Low-Light Camera's audio](https://github.com/bluerobotics/companion/blob/master/tools/audio.py). Would be good to support at least that, but preferably just audio streaming and recording in general (assuming that's possible).

Internal discussion [here](https://bluerobotics.slack.com/archives/C02UF32NXN0/p1646967559415739), which mostly covers:
- QGC currently doesn't have audio support, although [there is an issue about it](https://github.com/mavlink/qgroundcontrol/issues/7308)
- BlueOS builds gstreamer from source, and may not have the [`alsasrc`](https://gstreamer.freedesktop.org/documentation/alsa/alsasrc.html) element as a result
- audio support likely makes the most sense in [mavlink-camera-manager](https://github.com/bluerobotics/mavlink-camera-manager) (which BlueOS uses), but adding it would likely require some API changes, and may not be super simple to do
- definitely a useful feature to some users, but also not critical functionality to _most_ users

### Prerequisites

- [X] I have checked to make sure that a similar request has not already been filed or fixed.