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.

"""Clears the DagRun."""
        dag_id = request.form.get("dag_id")
        dag_run_id = request.form.get("dag_run_id")
        confirmed = request.form.get("confirmed") == "true"
        dag = get_airflow_app().dag_bag.get_dag(dag_id)
        dr = dag.get_dagrun(run_id=dag_run_id)
        start_date = dr.logical_date
        end_date = dr.logical_date
        return self._clear_dag_tis(
            dag,
            start_date,
            end_date,
            origin=None,
            recursive=True,
            confirmed=confirmed,
            session=session,
        )
    @expose("/blocked", methods=["POST"])
    @auth.has_access(
        [
            (permissions.ACTION_CAN_EDIT, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG_RUN),
        ]
    )
    @provide_session
    def blocked(self, session: Session = NEW_SESSION):