Win explorer context menu fix

This change is to fix the KDiff3 right-click context menu to start showing up in Windows Explorer again. The issue was, when kdiff3ext.dll was loaded by Windows Explorer, it would try to load some dependent DLLs, the first one being QT5Core.dll. However, since those dependent DLLs were in a different directory (KDiff3\bin) than kdiff3ext.dll (KDiff3\bin\kf5), they were not found. Now, kdiff3ext.dll will be moved out of the kf5 subdirectory, so that dependent DLLs will be found when it loads.

This change also requires a corresponding change in this file in the craft-blueprints-kde repo: https://invent.kde.org/packaging/craft-blueprints-kde/-/blob/master/extragear/kdiff3/kdiff3.py

I can open the necessary merge request in craft-blueprints-kde if you agree this change makes sense.