Add focus support for SurfaceControlViewHost

This change introduces a new call for clients to request focus on their
embedded views. In order to accomplish this, the owner of the
SurfacePackage sends an input token that can identify the input channel
of the embedded window. This token is forwarded as part of the focus
request.

WindowManager will authenticate the calling window and the relationship
between the host and the embedded window. Once authenticated, the
request will be forwarded to InputDispatcher. InputDispatcher will grant
the focus to the SurfaceControlViewHost if the host window is currently
focused or transfer focus back to the host window if the
SurfaceControlViewHost is focused. Otherwise the request is dropped.

In addition, SurfaceView, the host in this scenario, now overrides the
onFocused function to transfer focus to and from the embedded view.

Test: atest SurfaceControlViewHostTests
Bug: 151179149

Change-Id: Ia95545a60d73db4c03679bce9747d2e275806838