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.

else:
            final_task_instance_query_result = running_task_instance_query_result.subquery("final_ti")
        qry = (
            session.query(
                final_task_instance_query_result.c.dag_id,
                final_task_instance_query_result.c.state,
                final_task_instance_query_result.c.is_dag_running,
                sqla.func.count(),
            )
            .group_by(
                final_task_instance_query_result.c.dag_id,
                final_task_instance_query_result.c.state,
                final_task_instance_query_result.c.is_dag_running,
            )
            .order_by(
                final_task_instance_query_result.c.dag_id,
                final_task_instance_query_result.c.is_dag_running.desc(),
            )
        )
        data = get_task_stats_from_query(qry)
        payload: dict[str, list[dict[str, Any]]] = collections.defaultdict(list)
        for dag_id in filter_dag_ids:
            for state in State.task_states:
                count = data.get(dag_id, {}).get(state, 0)
                payload[dag_id].append({"state": state, "count": count})
        return flask.json.jsonify(payload)
    @expose("/last_dagruns", methods=["POST"])
    @auth.has_access(
        [
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),