Add "Configure Displays" action to desktop context menu
This is a resubmitted version of !704 (closed) with a bit of code cleanup and the kind of plausible-seeming bug-focused justification that was requested in https://bugs.kde.org/show_bug.cgi?id=355679. :) I have retained @ebuka's authorship information as he did most of the work.
For completeness's sake, I have also submitted a companion MR to add a button to open the KScreen KCM onto the Edit Mode toolbar: plasma-desktop!613 (merged)
With a multi-screen setup, it's possible to get into a situation where all of your means to launch apps have gone missing because a screen forgot its containmewt or moved the only panel onto a disabled output, or any number of other issues that unfortunately have not yet been resolved. In such a situation, it is common for people to try to fix it by visiting the KScreen KCM to switch around their primary screens, enable disabled outputs, turn it off and on again, etc.
However if your only visible means to launch apps has gone missing, you may have a hard time accessing the KScreen KCM. In such a circumstance, it can be helpful to have the action in the desktop context menu so that people can right-click on the wallpaper of any screen that is working and make System Settings launch with the KScreen KCM on that screen.
Co-authored-by: Nate Graham firstname.lastname@example.org
BUG: 355679 FIXED-IN: 5.24