Editor Preference settings get wrongly saved within project instead of editor

Various settings within the Editor Preferences window get saved within the project instead of the Editor. If someone were to heavily modify their Editor Preferences they would have to set it up again with each project they work on.

This issue was reported and tested in 4.20 (CL-4212847) and reproduced in 4.19.2 (CL-4033788) and Main 4.21 (CL-4221482)

1. Open the UE4 Editor and create a new project
2. Open the Editor Preferences window
3. Go to Level Editor > Viewports, and enable Invert Middle Mouse Pan
4. Go to Content Editors > Graph Editors > Splines. Click the arrow for 'Show Advanced' and modify any of the settings there.
5. On the top right, click the "Set as Default" button. If it asks you to make config file writable, do so.
6. Create another, different new project

Results: Invert Middle Mouse Pan and Graph Editors spline options changes are not propagated into a new project despite changing them in Editor Preferences and clicking "Set as Default"

Expected: Invert Middle Mouse Pan, Spline, and pretty much any options found in Editor Preferences is saved globally within the Editor, regardless of the project.