The DAGs main page has All/Active/Paused.

It would be nice if we can have also Running Now which will show all the DAGs that have at least 1 in Running of DAG runs:
![Screen Shot 2021-08-25 at 11 30 55](https://user-images.githubusercontent.com/62940116/130756490-647dc664-7528-4eb7-b4d8-515577f7e6bb.png)


For the above example the new DAGs tab of Running Now should show only 2 rows.
The use case is to see easily what DAGs are currently in progress.

nodes_dict: dict[str, Any] = {}
        edge_tuples: set[dict[str, str]] = set()
        for dag, dependencies in SerializedDagModel.get_dag_dependencies().items():
            dag_node_id = f"dag:{dag}"
            if dag_node_id not in nodes_dict:
                nodes_dict[dag_node_id] = node_dict(dag_node_id, dag, "dag")
            for dep in dependencies:
                if dep.node_id not in nodes_dict:
                    nodes_dict[dep.node_id] = node_dict(dep.node_id, dep.dependency_id, dep.dependency_type)
                edge_tuples.add((f"dag:{dep.source}", dep.node_id))
                edge_tuples.add((dep.node_id, f"dag:{dep.target}"))
        self.nodes = list(nodes_dict.values())
        self.edges = [{"u": u, "v": v} for u, v in edge_tuples]
def add_user_permissions_to_dag(sender, template, context, **extra):