Port VV preferences from GtkComboBox to AdwComboRow
This removes another `GtkComboBox` and fixes the requested width of the row, so the label no longers gets squashed when you have a long device name.
Testing Done:
Opened Prefs, selected a different Audio Input, and confirmed it was saved/restored when re-opening.
Ran Test Audio and confirmed input was coming from the right input.
Disconnected an audio device and confirmed that the list re-populated correctly.
Disconnected the *selected* audio device and confirmed that the selection dropped back to Default.
Ran Test Audio, disconnected the selected audio device and confirmed the audio pipeline switched to Default device.