Port SurfaceControlViewHost to BLAST

This is mostly a matter of flipping the flag, except for the case of
SystemWindows. While external SurfaceControlViewHost clients use the
leash provided by the SurfaceControlViewHost rather than the internal
ViewRootImpl surface, SystemWindows clients will use the actual
ViewRootImpl surface. This can conflict with the BLAST adapter setting
crop/frame/etc on this Surface. We modify SystemWindows to put
each layer inside a leash, and hand this out to other parts of SysUI
instead of the ViewRootImpl surface.

Test: Existing tests pass
Bug: 168505645
Change-Id: Ie621f89166f00ce385d450f1f1cea4d4abd1b805