floss: Attach the absolute_volume to BluetoothAudioDevice

The absolute volume support should be sent along with the
BluetoothAudioDevice to fix the issue that AvrcpAbsoluteVolumeEnabled
is triggered before the HFP and A2DP are both ready or timeout. This
will cause the audio client miss the absolute_volume_supported_changed
event.

Tag: #floss
Bug: 229781949
Test: build, deploy, connect and check the dbus_monitor output.
BYPASS_LONG_LINES_REASON: Bluetooth likes 120 char lines

Change-Id: Ic5bf04c01ba03897410df1945374570b21261aad