QmlDesigner: Add environment and model selectors to material preview

The model and the scene environment used to render material previews
can now be selected via buttons next to the preview in material editor.

Task-number: QDS-7347
Change-Id: I03089029e8420f80ed65be1c7b7a1ce4581f2fd4
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/plugins/qmldesigner/components/materialbrowser/materialbrowserview.cpp

@@ -284,6 +284,10 @@ void MaterialBrowserView::customNotification(const AbstractView *view, const QSt
         int idx = m_widget->materialBrowserModel()->materialIndex(nodeList.first());
         if (idx != -1)
             m_widget->materialBrowserModel()->selectMaterial(idx);
+    } else if (identifier == "refresh_material_browser") {
+        QTimer::singleShot(0, this, [this]() {
+            refreshModel(true);
+        });
     }
 }