Fix desktop launch (unminimize) animation scaling.

Before this CL the scaling in window WindowAnimator was only working
correctly for closing/minimizing windows. For opening/unminimizing
windows the scale would be 1 during the entire animation.

Also
1. animate over the window position (PointF) instead of the window
   bounds (Rect) to make it clear that we're not actually using the
   bounds themselves during the animation, and
2. update WindowAnimatorTest to check the position and scale of the
   actual transaction rather than the animated rectangle values.

Test: WindowAnimatorTest
Bug: 327428659
Flag: com.android.window.flags.enable_desktop_app_launch_alttab_transitions
Change-Id: Ibf58ddb044c5e2078beb6fc26fedbb5b7df3ba25