Blur the root window view when we transition from GlanceableHub to PrimaryBouncer

This is not an issue as of now as we don't see wallpaper when bouncer is opened from the glanceable hub, but if UX decides to not show the glanceable hub behind the bouncer then we'll end up showing the unblurred wallpaper.

Bug: 381263344
Test: unit tests
Flag: com.android.systemui.bouncer_ui_revamp
Change-Id: I633b492ca4cdbc38a34156678a8a6467b0a13208