Adopt floating version of VerticalExpandContainerSpec on split shade

- This is a initial experiment on how to implement the different
  behaviors, I intend to iterate on this more.
- Switches the test runner to ParameterizedAndroidJunit4, and renames
  the existing goldens. Due to b/402331022, the golden names have to be
  specified explicitly now

Bug: 401224916
Test: ContentRevealTest
Flag: com.android.systemui.scene_container
Change-Id: Ia99a01f5a419ee52c4f3646f912e6de0cf61d739