Clean up the animation of surfaces behind Keyguard on unlock.

This does a few things:
1. Unifies the behavior before and after the Keyguard root view is
   gone (before some values were different) to match the unflagged
   behavior. An exception to this is the amount of the translation,
   which is controlled outside of this applier.
2. Clean up some magic numbers.
3. Move the translation inside the matrix. Before, `setTranslate()`
   was overridden by the following `setMatrix`().
4. Ensure that the translation percentage is calculated correctly, so
   that the scale is also correct for the whole duration.

Fix: 438430688
Flag: com.android.systemui.keyguard_wm_state_refactor
Flag: com.android.systemui.scene_container
Test: manual (see video in the bug)
Change-Id: I25414b5e59865a8000400df93cc5c63a35f74a7a