API for enumerating and selecting an audio output

[SolarLiner]

Summary

Currently, if users want to output to a specific audio device, they need to manually give it in the backend settings. It's a bit too low level for general usage, and we should have a way to make it so that the audio device can be easily enumerated (to allow building settings UIs) and set.

Note that Kira does not support changing the audio device after having created the audio engine.