Include previous parent work item within response of workItemsHierarchyReorder mutation

Summary

The workItemsHierarchyReorder includes parentWorkItem field which represent the parent of a work item after the reorder operation is successful, but since the mutation may be slow in certain situations, we can leverage optimistic update of VueApollo to improved perceived performance of the reorder operation and in order to do that, we also need mutation to include previous parent work item within the response.