[PIP2] Fix enter/exit animator

Fix issue with enter/exit animation. This contains a bug
with the home screen not drawing properly, will be investigated
separately. Also contains some skeleton code for fixed rotation,
which will be the follow up CL.

Test: enter exit in button nav, see video
Video: http://recall/-/cidfAmGe9UaIuFMHR3GEC8/gnO69ueSDM2VLcxnM4pY2p
Flag: com.android.wm.shell.enable_pip2_implementation
Bug: b/350801661
Change-Id: I9a431324ba59301c85c00f08047e5f654322316b