Prepare for LayoutTransition with RTL support.

Only remove divider when it needs to be removed or moved between All Apps and recents locations. Keep All Apps and QSB in Taskbar at all times. LayoutTransition does not work if views are being removed and then immediately readded (what current code branch does).
Overflow is not supported yet with the LayoutTransition flag.

Test: go/tested-equals
Flag: com.android.launcher3.taskbar_recents_layout_transition
Bug: 368522274, 343521765
Change-Id: I9ae1d7c52e853106cdf86329be6f221213e7cb86