Introduce opt-out options to stable configuration

To avoid incremental breakages, re-use the e2e enforcement opt-out flag
to let the app developers opt-out the stable configuration change.

Besides, the change also updates the Display.getSize() API doc to
reflect the stable configuration change. And updated the API doc of
LAYOUT_IN_DISPLAY_CUTOUT_MODE_SHORT_EDGES flag to reflect the movable
display cutout change.

Bug: 332750049
Test: DisplayTests
Test: Set the flag and observe the behavior
Change-Id: I66f3dc52af822a4c9b4e49eafd118e9c078fcac2