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.

"""Redirect from url param."""
        return redirect(url_for("Airflow.duration", **sanitize_args(request.args)))
    @expose("/dags/<string:dag_id>/duration")
    @auth.has_access(
        [
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_TASK_INSTANCE),
        ]
    )
    @action_logging
    @provide_session
    def duration(self, dag_id: str, session: Session = NEW_SESSION):
        """Get Dag as duration graph."""
        dag = get_airflow_app().dag_bag.get_dag(dag_id, session=session)
        dag_model = DagModel.get_dagmodel(dag_id, session=session)
        if not dag:
            flash(f'DAG "{dag_id}" seems to be missing.', "error")
            return redirect(url_for("Airflow.index"))
        wwwutils.check_import_errors(dag.fileloc, session)
        wwwutils.check_dag_warnings(dag.dag_id, session)
        default_dag_run = conf.getint("webserver", "default_dag_run_display_number")
        base_date_str = request.args.get("base_date")
        num_runs = request.args.get("num_runs", default=default_dag_run, type=int)
        if base_date_str:
            base_date = _safe_parse_datetime(base_date_str)