Add autotaskstackcontroller.

- Provides opinionated APIs to implement task stack based windowing.
- Uses shell transitions to enforce a custom z-layer for the task stacks.

Flag: com.android.systemui.car.auto_task_stack_windowing
Test: m
Bug: 384082238
Change-Id: I8f4ee2c71a8d574694ef8eb0ee5ac54e474f0a6d