bluetooth: Add 'defaults' for 'android_hardware_bluetooth_audio'

Add defaults for the case when the library is used
from within 'target/android'.

Also, switch 'BluetoothLeAudioCodecsProviderTest' to use
'defaults' instead of hardcoding the interface module version.

Bug: 307310023
Test: m
Change-Id: I7e5e70efe6a733367a8b5cbe5cffbfddf610cc6b