plasmoidviewer: Sync to plasma-desktop

Hello, This MR sync shell configuration and applet with plasma/plasma-desktop.

This is basically an copy/paste of the files without the plasmoid.configuration.writeConfig() lines.

PS: I'd be happy if the translation bug could be fixed 😉 src: https://invent.kde.org/plasma/plasma-sdk/-/blob/master/plasmoidviewer/view.cpp?ref_type=heads#L111-116