Add support for Multi-A2DP state machines per device

Update usage of A2dpService API calls that take BluetoothDevice
as an additional argument. If the BluetoothDevice argument is null,
the API applies to the device that is currently the Active A2DP device.

Bug: 69269748
Test: Manual
Change-Id: I8031fa4b4256890dcb486228185baf93debb102d
Merged-In: I7417b7b0741f706df475cb2b27fbe6525f744269