ScreenDecor: Set touchable region in windows coordinate space

Also restricts the region to the frame of the view. This
is important for double cutouts, would go to the wrong view,
and having a touchable region spanning the entire screen
breaks some a11y services.

Change-Id: I824e5fb9b2f2e765ee9b6da4fcaf2c6840d8f51d
Fixes: 79533418
Test: turn on double cutout emulation; adb shell dumpsys window ScreenDecor, verify touchable region for each decor looks right.