Fix two bugs with rotation in split select state

This CL fixes two bugs that were triggered by rotating in split select state:
1) Rotating in split select state will no longer cause a jittery animation to play
2) Initiating split from home, then rotating will no longer create extra split placeholders on screen

The bugs were present because handleSplitSelectionState() animated every state transition into SplitSelect, including SplitSelect > SplitSelect (which happens when rotating). This caused a jittery animation to play, and in certain cases, caused additional copies of FloatingTaskView and SplitInstructionsView to be created.

Fixed by auto-skipping animations for SplitSelect > SplitSelect, and by safely removing views when entering SplitSelect (to prevent duplicates).

Fixes: 242965515
Fixes: 243088958
Test: Verified visually on-device.
Change-Id: Iab813b1fe599bfdc550fe9a1d354b28cedb4b659