Use blur scale to apply depth push on hub transition

This change refactors an ealier motion change ag/34260411.
Instead of handling wallpaper zoom-out separately, we're now integrating
the zoom-out transition animation, directly into the cross-window blur
for hub transitions.
Then the zoom-out flows are wired up to WindowRootView#blurScale, so
that blur radius and scale can be performed together.

Bug: 404535174
Test: atest WindowRootViewModelTest
Flag: com.android.systemui.gesture_between_hub_and_lockscreen_motion
Change-Id: I1b0b8636defcf0d4f3684a12e867367e479f73fb