Allow use of mouse wheel while re-ordering layer in tree

[nicogodet]

Feature description

Currently, if a layer need to be moved to a non visible group (because too far above or below current position), user need to drag the selection to the edge of layer tree widget, wait for automatic pan to reach the desired location.

It can be very slow in case of crowded project.

Use of mouse wheel while dragging selection will be mush more efficient.

Additional context

No response