Show split select instructions toast when starting split on workspace

* Used same animation properties that RecentsView uses to
show the instructions view unfolding
* TODOs:
  * UI polish (correct asset, animation timings, etc)
  * Hook into existing animations (if possible)
  * Migrate recentsView splitInstructionsView to use same/similar code path;
    remove RecentsView#safeRemoveDragLayerView

Bug: 276361926
Test: Create split w/ and w/o flag, works as expected
Flag: ENABLE_SPLIT_FROM_WORKSPACE_TO_WORKSPACE
Change-Id: I7a51b71c358902399ad73b650287cdbf1dad07c6