Since Wayland has per-screen scaling, make QuickEditor paint screen by screen.
Make adaptation consequently.
Add a dependency to KScreen to get the real hardware scaling (QScreen does not allow to get the real scaling on Wayland).
Adds a GrabMode::AllScreensNativeSize that the image should follow the pixel on screen output rather than the scaled output.
GrabMode::AllScreens now means grab image with scaled output.
It is useful in Wayland since the QuickEditor needs pixel-on-screen output but multi-screen screenshot wants scaled output that is not distorted.
Under X the two do the same since the scaling is the same on all screens, the pixel on screen output cannot be distorted.
Improve bottom Help text positioning in multi-screen.
See also D29122