Tweak notification scrim easing

A faster fade in that will help with:
- Avoid weird state where scrims and notifications overlap
- Better connection with launcher scrim (similar easing)
- Reduced overdraw, marking shade window as opaque earlier

Test: manual
Test: atest ScrimControllerTest
Fixes: 189118510
Change-Id: I47e357d1d6dd7ee8b8a0b68d37d808c85465375d