Combine launchBehind + solid color splash screen for back predictive.

Address for no snapshot case.
To reduce the possible flickering caused from the icon of splash
screen, using solid color splash screen surface for opening target, and
set launchBehind for the opening activity.
Once the activity has drawn, remove the splash screen surface.

Bug: 268563842
Test: disable record snapshot and enable predictShowStartingSurface.
Verify predictive back animation will first show splash screen surface
for the opening target, then shows app window once it report drawn.

Change-Id: I14f20b1c69874661f91da6e299e63e6c2d0d32ee