monitors/bluez: fix autoswitch A2DP input profiles
Profile autoswitch should support also A2DP profiles with input route, so the loopback should not assume the source node is SCO one.
Also fix handling of AG SCO output stream nodes, which should not be hidden as internal.
autoswitch-bluetooth-profile: never use headset profile without input
Autoswitch should make sure the saved headset profile always has an input route. Check this on loading/saving it, otherwise reselect it.
Headset mode profile without mic used to make some sense when it wasn't using the loopback node (ie. easy way to disable it), but now with the loopback node this doesn't make sense any more and it's confusing if it occurs, so we shouldn't allow it.