Send device connection intents from AudioService

AudioService is currently notified of wired headset and A2DP
sink connection states via broadcast intents from WiredAccessoryObserver
and BluetoothA2dpService. This is a problem as there is no guaranty that
AudioService can take actions upon the change before other apps are notified.
For instance, the Play On feature requires the UI to be refreshed when a device
is inserted/removed and we must guaranty that the UI component can read
new A2DP enable state from AudioManager after it receives a device connection state
change intent.

- Added hidden methods to AudioManager so that WiredAccessoryObserver
and BluetoothA2dpService can notify AudioService of device connection directly.
- The wired accessories connection intents are now sent by AudioService.
- The A2DP state change intent is delayed by BluetoothA2DPService when
ACTION_AUDIO_BECOMING_NOISY is sent by AudioService
- ACTION_AUDIO_BECOMING_NOISY intent is not sent when disconnecting A2DP
while a wired headset is present and vice versa.

Bug 6485897.

Change-Id: Ie160b3ee5f451132065530772b868593c90afd94