Blur the notification scrim when we open the scrimmed bouncer from shade

Previously we were hiding (alpha to 0) it when scrimmed_bouncer was opened, the scrim view was not blurred and its outline would show up prominently behind the bouncer.
Other changes:
 1. Make the shade blur match the max blur radius as per spec.

Bug: 391409919
Test: verified manually,
 1. Expand shade
 2. Tap on notification
 3. Observer that the blur looks normal behind the bouncer.
Flag: com.android.systemui.bouncer_ui_revamp
Change-Id: I5ffec31c42b07c9f651cb2d19667cb172c56ff44