Work items list [BE] - Allow reordering of work items (for Manual sort on work items list)

On both the legacy project and group issues list, you can select the Manual sort order and reorder issues with drag-and-drop. The frontend sends a PUT request to an endpoint like http://127.0.0.1:3000/flightjs/Flight/-/issues/29/reorder.

For issues list parity, we need to allow the same functionality for the project and group work items list. We should add a GraphQL mutation that allows us to reorder work items.