SurfaceControlViewHost: Add side-channel to SurfacePackage

We add a control interface in to surface-package which allows
the embedding process to dispatch events back to the embedded
process. So far we support forwarding configuration changes,
and dispatching a detach view hierarchy message.

Bug: 213603716
Test: Existing tests pass
Change-Id: I7d68628d845b5da687568ffa20529ce2a7772495