Optimization in KDE Base
Simplify insertion index calculation for DND reordering.
The original code took a stab at there being some travel resistance
to drags to avoid undesired accidental moves, but aside from doing
this in a naive (and buggy) way, it also turns out to be unnecessary
in further testing: Drag initiation has resistance to it anyway, and
during moves, the lack of resistance makes accidental overshoots
easy to correct for, along with the upside of making DND feel much