ICore: Change some path API to use FilePath

Change-Id: Id841d6177206a021c9e606ce560b47d1ae6e52b9
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: hjk <hjk@qt.io>

src/plugins/studiowelcome/examplecheckout.cpp

@@ -65,8 +65,10 @@ void ExampleCheckout::checkoutExample(const QUrl &url)
     layout->addWidget(widget);
     widget->engine()->addImportPath("qrc:/studiofonts");
 
-    widget->engine()->addImportPath(Core::ICore::resourcePath()
-                                    + "/qmldesigner/propertyEditorQmlSources/imports");
+    widget->engine()->addImportPath(
+        Core::ICore::resourcePath()
+            .pathAppended("/qmldesigner/propertyEditorQmlSources/imports")
+            .toString());
 
     widget->setSource(QUrl("qrc:/qml/downloaddialog/main.qml"));