QS: Fix up Wifi Display tile for screencasting and reenable it

Replace the Wifi Display code with MediaRouter/RemoteDisplay observers,
and turn let the controller manage the tile again

Change-Id: Iaf5c509ae078b9305d1d314ec76d44362beb025e
QS: Rename WiFiDisplay to RemoteDisplay

Change-Id: Iae8537482bc2c2a1beca71336a569bc5d4c16df5