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.

state_color_mapping = State.state_color.copy()
        state_color_mapping["null"] = state_color_mapping.pop(None)
        page_title = conf.get(section="webserver", key="instance_name", fallback="DAGs")
        page_title_has_markup = conf.getboolean(
            section="webserver", key="instance_name_has_markup", fallback=False
        )
        dashboard_alerts = [
            fm for fm in settings.DASHBOARD_UIALERTS if fm.should_show(get_airflow_app().appbuilder.sm)
        ]
        def _iter_parsed_moved_data_table_names():
            for table_name in inspect(session.get_bind()).get_table_names():
                segments = table_name.split("__", 3)
                if len(segments) < 3:
                    continue
                if segments[0] != settings.AIRFLOW_MOVED_TABLE_PREFIX:
                    continue
                
                yield segments[-1], table_name
        if (
            permissions.ACTION_CAN_ACCESS_MENU,
            permissions.RESOURCE_ADMIN_MENU,
        ) in user_permissions and conf.getboolean("webserver", "warn_deployment_exposure"):
            robots_file_access_count = (
                session.query(Log)
                .filter(Log.event == "robots")
                .filter(Log.dttm > (utcnow() - datetime.timedelta(days=7)))
                .count()
            )
            if robots_file_access_count > 0:
                flash(