Apply front scrim to doze pulsing

When ambient goes dark, apply the same front scrim opacity during doze
pulsing. The would then be a common behavior to all pulsing reaons.

Bug: 139445074
Test: Manual tests
Test: atest ScrimControllerTest
Change-Id: I3f1f7ca00b9d200ce4a7120b5328527ab9d9fb13