Prior behavior for interactive area split would create the new area
immediately. If pulled from the top the new area would be above, while
if pulled from the bottom the new area would always be below. With
docking the split does not occur until the end, which would reverse
the area orders if the split was larger than 50%. This PR creates with
the old expected order, based on the starting position.
Pull Request: https://projects.blender.org/blender/blender/pulls/125338
f6ae3bf8f3