Add corner radius for PiP window

Per UI/UX, the radius is fixed to 8dp, configurable in SystemUI
resources. Also included in this CL:
- deprecated scheduleFinishEnterPip with a more meaningful transition
direction @IntDef
- consolidate the parameter orders in PipTaskOrganizer,
    Sf.Transtion > from / to bounds > direction > duration > others

Screenshot
- https://screenshot.googleplex.com/y67xOhM7Hxt.png
- https://screenshot.googleplex.com/EUvw63Y8ckY.png

Bug: 137390622
Test: Enter/expand/collapse PiP
Test: atest PipAnimationControllerTest
Test: atest PinnedStackTests
Change-Id: I87231746b34c36eba6aaec77b61c9249e835fd47