Allow 3p apps to hide non system overlay windows

SAW permission is added to the shell to allow it to create
TYPE_APPLICATION_OVERLAY windows during testing.

Test: atest CtsWindowManagerDeviceTestCases:HideOverlayWindowsTest
Bug: 159616727
Change-Id: I503cd8da24ff4d2b928f930ac61090e6782c1546
6 files changed