Disallow applications from initiating cast screen.

Only allow the system ui and settings to connect to a remote display.
To do this, we essentially hide the remote displays from applications
by using the ROUTE_TYPE_REMOTE_DISPLAY then add permission checks
around the operations that connect to them.

As a bonus, this may actually save power on devices since applications
that use MediaRouter will not longer be performing discover on
remote display routes at all.

Bug: 11257292
Change-Id: I9ea8c568df4df5a0f0cf3d0f11b39c87e2110795