SurfaceControlViewHost: Allow updating of WindowContext used for SCVH

Our initial attempt to allow updating the configuration of
SurfaceControlViewHost was insufficient when the SurfaceControlViewHost
is using a service context. This service context will always be
on the global configuration, and ViewRoot won't be able to override it.
We add some documentation suggesting the user use a window context,
and wire up SurfaceControlViewHost VRI so that they are the authority
on configuration (and propagate the change in to the context).

Bug: 215204813
Test: SurfaceControlViewHostTests. Manual in game overlay+split-screen
Change-Id: I24c0309593b7fddaeab8db355f63a5f6bd763562