Fix split animation with small number of tasks only

- Extract newClearAllShortTotalWidthTranslation out from the last grid task visible case, to use it to predict new clearAllShortTotalWidthTranslation after focus task is staged, then use newClearAllShortTotalWidthTranslation to compensate getScrollForPage of grid tasks not on top-right corner for tasks close to clearAllButton
- Applied ag/28945919's fix to dismiss animation as well
- Fixed next focused task translation using wrong sign in RTL

Fix: 378403770
Test: With LTR/RTL, test focused task staging / dismiss with 1-6 tasks, dismiss grid end tasks with 1-6 tasks
Flag: EXEMPT BUG_FIX
Change-Id: Ie5b597c4318c5de84377fde50090491e78581af9