DisplayCutout: account for cutout in appWidth/appHeight etc.

Makes sure to take into account the area blocked by the cutout when
calculating the nonDecor / config / stable insets, widths and heights.

Fixes: 72995358
Fixes: 72444324
Test: atest PhoneWindowManagerInsetsTest
Test: go/wm-smoke
Test: Enter splitscreen, verify that both windows are same size

Change-Id: Iff58235b5bdfd0d49df259a91b05e54e3864f41c