SurfaceControl: Add setDropInputMode api

Introduces an API to drop input events on this SurfaceControl. This
policy will be inherited by its children. The caller must hold the
ACCESS_SURFACE_FLINGER permission.

Options include:
ALL: SurfaceControl and its children will not receive any
input regardless of whether it has a valid input channel.
OBSCURED: SurfaceControl and its children will not
receive any input if the layer is obscured, cropped by its parent or
translucent.

These policies are used to enable features that allow for a less trusted
interaction model between apps. See the bug for more details.

Test: atest libgui_test InputDispatcherDropInputFeatureTest
Bug:197364677

Merged-In: Ifcb4133306a43874e74e8fb0f42b60842daf6f25
Change-Id: Ifcb4133306a43874e74e8fb0f42b60842daf6f25