Android: Better device discovery of audio output

Audio device enumeration is a bit unclear on Android. Some devices will only expose a single "built in speaker" device and will automatically switch device under-the-hood if the user plugs in external devices (i.e headphones). On some of my other devices (i.e Motorola Razr 40 Ultra), it exposes two devices "built in earpiece" and "built in speaker" at all times, but these behave the exact same. (I would argue this is a bug)

The effect is that audio playback powered by Qt will go through whatever device the system considers default. Other applications, such as Teams and Discord are able to correctly enumerate audio output devices and allows the user to select which one should output the audio for the given application.

Qt should be able to power this usecase in order to be competitive with other mobile frameworks.

Note: This might apply to microphone devices also, but I was not able to find applications that could choose microphones individually.

Note: Only tested on FFmpeg backend