Bug 5300223 RemoteControlClient uses PendingIntent for media button events

Update the implementation of the RemoteControlClient / Display
 feature rely on PendingIntent as provided in the construction
 of the RemoteControlClient instance.
The ComponentName that describes the target of the media button
 events is set as the target of the Intent from which
 a PendingIntent is constructed.
This ComponentName is still saved in the stack for persisting
 the last media button event receiver.

This CL also updates the lockscreen IRemoteControlDisplay
 implementation to use the PendingIntent supplied by the
 application when sending transport control events. A (good)
 side effect of doing this is that intent will be directly
 targeted at the application.

Restoration of the media button event receiver
 after reboot is not fully functional yet.

Change-Id: I2be82f2839e9dee1de02512437b3fb41cc386cde