Accelerate wallpaper unlock transition

Flagged version of ag/24904329.

With this CL:
  - The lock wallpaper fade out starts with no delay, as soon as the
    shade starts to disappear, and lasts 83ms in total
  - The home wallpaper fade in starts after a short delay of 67ms, so
    the lock wallpaper is almost gone when the home wallpaper appears.
    The fade in total duration is 167ms

Flag: ACONFIG com.android.systemui.Flags.fast_unlock_transition DEVELOPMENT
Bug: 298186160
Test: manual
Test: atest KeyguardUnlockAnimationControllerTest
Change-Id: I33af089261c99e319298015a766a165b0400f9cb