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.

return self.render_template(
            "airflow/chart.html",
            dag=dag,
            root=root,
            form=form,
            chart=Markup(chart.htmlcontent),
            tab_title="Tries",
            dag_model=dag_model,
        )
    @expose("/landing_times")
    @auth.has_access(
        [
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_TASK_INSTANCE),
        ]
    )
    @action_logging
    def legacy_landing_times(self):
        """Redirect from url param."""
        return redirect(url_for("Airflow.landing_times", **sanitize_args(request.args)))
    @expose("/dags/<string:dag_id>/landing-times")
    @auth.has_access(
        [
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_TASK_INSTANCE),
        ]
    )
    @action_logging
    @provide_session
    def landing_times(self, dag_id: str, session: Session = NEW_SESSION):