Add field to set A2DP device volume on connect (1/2)

Add a field to setBluetoothA2dpDeviceConnectionStateInt() to allow
Bluetooth to set a volume for the new device when it connects.

Bug: 79529581
Test: Switch repeatedly between devices and see that the old volume isn't
used on the new device or the new volume isn't used on the old device.
Change-Id: I909fa3f40818c595fc977695fbfa1214f9a4de72