QmlDesigner: Restore auxiliary properties after rewriter model attach

Successfully restoring auxiliary properties requires scene model to be
complete, so we must wait until model is attached.

Fixes: QDS-12615
Change-Id: I906e9b50df14fcdbc0cad8370c5466db5c1aab02
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>
(cherry picked from commit 7ba7624bb6)

src/plugins/qmldesigner/designercore/model/rewriterview.cpp

@@ -104,6 +104,7 @@ void RewriterView::modelAttached(Model *model)
         m_modelAttachPending = true;
         QTimer::singleShot(1000, this, [this, model](){
             modelAttached(model);
+            restoreAuxiliaryData();
         });
     }
 }