[PANDORA_TEST] Update a2dp method to use a device

Android interface is made with BluetoothDevice in mind. We should
interact with it using this data type instead of an address. This CL
remove the usage of any address to directly use a BluetoothDevice.

Editting the cookie in Source & Sink in order to be a connection
instead. This allow to use the same method to get the BluetoothDevice
and reduce the different message type we are using

Remove wrappers in a2dp.proto that was generating a non-used warning

Bug: 237447510
Test: atest pts-bot:A2DP
Test: atest pts-bot:AVDTP
Change-Id: I77da2f446799a92af256a31d63127cea42359f01