Revisit audio routing policy when disconnected

1) Activate the lastly activated device among currently activated
   devices
2) Activate the lastly activated device among currently connected
   device
3) Activate the built-in earpiece for calls, or the built-in speaker
   for other cases.

Bug: 299023147
Bug: 300174072
Test: atest BluetoothInstrumentationTests
Change-Id: I492d54b329e1f434d7e077db3cd98ec1c853a016