fixes #14139

- allows one to continually open files while keeping quick open widget focused
- uses the right modifier key to open in background
- can open in split view if using the cmd trigger key

Fixes #14060

This change does the following:
- filesToRestore are no longer checked at all, instead the the already existing
  editorStacks.model value from local storage restores the files just like
  normal.
- Loading of the resource is now solely the responsibility of
  TextFileEditorModel, removing a lot of the stuff being passed down through
  the layers.

Fixes #14100
Fixes #14067

See #12400 & #13305