QAudioDevice: Introduce ConnectionType property

Some mobile application with multimedia capabilities tend to have a audio output device picker that uses a different icons based on the connection type of the device. Examples include built in speaker, build in earpiece, USB and Bluetooth. Ideally, Qt should be able to power applications like these.

It would also allow us to improve how we name devices on Android especially. Currently on Android, device descriptions usually follow the pattern "Bluetooth (Actual device name)" or "Built in speaker (Phone name)". If we expose connection type as a separate variable, we can possibly provide a better naming scheme.

We should be able to implement this reliably for Android. We should do research to see if we can do this on other platforms as well. For platforms where it's not possible to determine, we can have a type "Unknown".