Split-shade: fix notification scrim position when there is a horizontal display cutout.

Notification scrim coordinates were being set without taking into
account horizontal insets coming from display cutouts such as notches
or cameras.

Test: manually on-device. Setting a handheld device to have smallest
width of 600dp and rotating it horizontally in both directions.
Fixes: 231769989

Change-Id: Ie19195ea5c76729a6795c6ebac263ec591b7d2e2