QmlDesigner: Update expand state upon renaming

Upon renaming an asset folder, update the expand state so that the
renamed folder receives the correct expand state.

Task-number: QDS-6200
Change-Id: I9868cb3e342a8a8488ed0b5a62735bc8af468dfe
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/qmldesigner/components/assetslibrary/assetslibrarymodel.cpp

@@ -144,6 +144,9 @@ bool AssetsLibraryModel::renameFolder(const QString &folderPath, const QString &
         return true;
 
     dir.cdUp();
+
+    saveExpandedState(loadExpandedState(folderPath), dir.absoluteFilePath(newName));
+
     return dir.rename(oldName, newName);
 }