RunnerModel: Display KCMs right after application results

A few KDE versions ago, the KCM and app results were provided by the same plugin.
To make sure they do not appear very far down the list, the plugin id is inserted right after the services runner.

CCBUG: 446239

applets/kicker/plugin/runnermodel.cpp

@@ -241,6 +241,7 @@ void RunnerModel::matchesChanged(const QList<Plasma::QueryMatch> &matches)
         const static QStringList runnerIds = {
             QStringLiteral("desktopsessions"),
             QStringLiteral("services"),
+            QStringLiteral("krunner_systemsettings"),
             QStringLiteral("places"),
             QStringLiteral("PowerDevil"),
             QStringLiteral("calculator"),