Fix TaskView jumping caused by split select

- Never apply split select translation to grid overview, instead use dismiss translation to make space to split placeholder to minimize motion and avoid janky double movement
- Ensures snapping to last task for end of grid split cases
- Adjust mCurrentPageScrollDiff due to coordinate shift
- Use longGridRowWidthDiff to shift all task to make space for split placeholder
- Also fixed a bug that split translation isn't reset if entering overview immediately after exit

Bug: 200537815
Test: manual
Change-Id: Ie1b57c34ce4bb079f898ba5b7c3464a714021847