cups: add comprehensive CUPs setting page

- Add printers
- Delete printers
- Use polkit APIs as fallback on auth errors
- Fix ref system to conditionally subscribe to cups when wanted

quickshell/Modules/ControlCenter/Models/WidgetModel.qml

@@ -41,16 +41,10 @@ QtObject {
 
         onItemChanged: {
             root.cupsBuiltinInstance = item;
-            if (item && !DMSService.activeSubscriptions.includes("cups") && !DMSService.activeSubscriptions.includes("all")) {
-                DMSService.addSubscription("cups");
-            }
         }
 
         onActiveChanged: {
             if (!active) {
-                if (DMSService.activeSubscriptions.includes("cups")) {
-                    DMSService.removeSubscription("cups");
-                }
                 root.cupsBuiltinInstance = null;
             }
         }