AudioService: fix disconnect/connect of A2DP device

 Due to the expected BECOMING_NOISY behavior associated
with a device disconnection, the disconnection is handled
asynchronously after a fixed delay. This delay caused an
inversion of commands in the processing order of the
disconnection of a device closely followed by connection
of the same device.
 The fix consists in:
- overriding the equals() operator for BtDeviceConnectionInfo
 so messages for a given device in the message queue
 can be checked / removed.
- when AudioDeviceBroker receives a command for A2DP
 connection or disconnection, remove all upcoming connection
 and disconnection commands in the queue for this device
 (see postBluetoothA2dpDeviceConnectionStateSuppressNoisyIntent)
- remove AudioDeviceBroker.handleSetA2dpSinkConnectionState, which
 was only used in BtHelper.onA2dpProfileConnected() with
 a CONNECTED state, and have this method perform a regular device
 connection (just like when coming from AM->AS).
- in AudioDeviceInventory.onSetA2dpSinkConnectionState(), support
 receiving a connection event for an already connected device,
 to support codec changes.

This change also includes modifications to the classes involved
in the device connection to make them support mocking/spying
to reproduce the bug conditions (see AudioDeviceBrokerTest).

Bug: 134932649
Test: atest AudioDeviceBrokerTest
Change-Id: If2b3b41409c77467a181a2f9b42310db9b9de8c5