Fix loading KCM in Plasma 6
metadata: Remove Id field
KPluginMetaData interprets the lib file name as the plugin id.
CMake: Sort some lists alphabetically
So that they are easier to scan through and modify/merge.
CMake: Remove unused linked library Qt::DBus
This KCM does not call or subscribe to any D-Bus services (although in future maybe it should).
CMake: Add CoreAddons to find_package explicitly
Port to new KCMUtils KCM classes
Note: porting kcm context property to KcmUtils.ConfigModule attached property was done to avoid undefined references in binging at unloading, such as closing kcmshell instance normally. Other uses were ported for consistency. Context traversing is slightly broken at initialization, which is why it has to be referred as root.* directly.