Omit hotspot offset for drag pixmaps in item views to make it easier to drop items in the correct location

The hotspot for drag pixmaps generated for item views is offset to appear aligned with the items in the view when the drag is initiated.

However, in most cases this means that the pixmap appears under the mouse cursor. This makes it difficult at best, and impossible at worst, to drop the items in the correct location, as it is not possible to see what is under the mouse cursor due to the offset pixmap.

If the pixmap is not offset, then the pixmap will appear to the bottom right of the cursor, making it much easier to drop the items in the correct location.

Note that this is not much of an issue on Mac, where the pixmap is partially transparent, thus it does not conceal whatever is under the mouse cursor. This is more an issue on Windows and X11.