Add API to allow SysUI/launcher to customize legacy task transition animations

Launcher needs to be able to customize the task transition to:

1. set the background color during task transitions to the taskbar color when the taskbar is visible.

and, temporarily, at least until tasks have rounded corners rather than being an overlay in the taskbar, we need:

2. a way to specify how much to crop the task by so that the task's rounded corners are visible above the taskbar during animation

3. a way to specify how much to crop the taskbar by so that the taskbar's rounded corners overlay is not visible over the tasks during the animation

Test: None
Bug: 200675009
Bug: 196387647
Merged-In: Ifb7f89e7fde47155eb987161fbbe30e7144103ab
Change-Id: Ifb7f89e7fde47155eb987161fbbe30e7144103ab