Don't send non-resizeable notification in some cases.

Don't send non-resizeable notification when putting other stacks in
the system in split-screen secondary windowing mode due to us entering
split screen mode since they won't be visible.

Also, added isVisible to containers in the window manager proto.

Change-Id: If83076514c160ad7b2a639e32d6f9fc85e70bd53
Fixes: 70355262
Test: go/wm-smoke and steps from bug.