Use android.media.audio.common.AudioDeviceAddress

Make sure that pairs of 'AudioDeviceDescription' (aka type) and
the device address are always represented in AIDL as AudioDevice.

Move all the AIDL<->legacy conversions into AidlConversion
so it is possible to switch to structured device address
representations in a subsequent CL.

Bug: 198812639
Test: m
Change-Id: If4300e411d76c90d42939f07298535ebdb4185f4