SurfaceFlinger-Input: Ignore invisible layers for occlusion detection

For legacy compatibility reasons, we allow apps to receive input prior
to submitting their first buffer, and for this reason we check
canReceiveInput() to populate InputWindowInfo#visible, rather than
directly calling isVisible(). However, in the case of layers which
can't receive input (!hasInputInfo()) and are exclusively being used
for occlusion detection we have no such legacy requirement and so we can just
directly check the visibility value. Obviously this doesn't
cause any problems with occlusion detection, since if the layer
isn't being drawn it can't occlude anything. This semantic is
very useful as it allows BufferLayers which no buffer drawn to be used
as ContainerLayers, as we frequently use SurfaceView for.

Bug: 157772682
Test: Existing tests pass.
Change-Id: Iadcd5d8fc4016ee1f88480a50bb3555797830560