Decoupling some drag and drop code handling

> Removing some special checks around accessibility drag
> Unifying folder alarm code path for accessible and normal DnD
> Maintaining mDragStartTime inside the dragDriver instead of the callers
> Simplifying some accessibility callbacks

Future cl will create a Accessibility DragDriver and unify it with
other DnD flow

Change-Id: I1919ef218de0174678110f271b450bcb9aaf4a5c