Blender Git Loki

Fix #30231: Drag and Droping Parenting from Outliner giving unnecessary Loop Error

In fact, error was much deeper and DND parenting in outliner used to parent all selected
objects to drop target, not just currently dragging object.

This was caused by code sharing between Parent Set operator and this DND operator which
was iterating all selected objects in scene and was setting parent to it.

Solved issue by separating actual parenting code which makes specified object be parented
to specified parent and moved iterating to Parent Set exec callback.

Now both of discovered issues (unneeded loop error and parenting all selected objects)
are solved, but more extensive testing of this changes are welcome.