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:
                dataset_triggered_next_run_info = {}
            for dag in dags:
                dag.can_edit = get_airflow_app().appbuilder.sm.can_edit_dag(dag.dag_id, g.user)
                dag.can_trigger = dag.can_edit and can_create_dag_run
                dag.can_delete = get_airflow_app().appbuilder.sm.can_delete_dag(dag.dag_id, g.user)
            dagtags = session.query(func.distinct(DagTag.name)).all()
            tags = [
                {"name": name, "selected": bool(arg_tags_filter and name in arg_tags_filter)}
                for name, in dagtags
            ]
            owner_links_dict = DagOwnerAttributes.get_all(session)
            import_errors = session.query(errors.ImportError).order_by(errors.ImportError.id)
            if (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG) not in user_permissions:
                
                import_errors = import_errors.join(
                    DagModel, DagModel.fileloc == errors.ImportError.filename
                ).filter(DagModel.dag_id.in_(filter_dag_ids))
            for import_error in import_errors:
                flash(
                    "Broken DAG: [{ie.filename}] {ie.stacktrace}".format(ie=import_error),
                    "dag_import_error",
                )
        from airflow.plugins_manager import import_errors as plugin_import_errors
        for filename, stacktrace in plugin_import_errors.items():
            flash(
                f"Broken plugin: [{filename}] {stacktrace}",
                "error",
            )
        num_of_pages = int(math.ceil(num_of_all_dags / float(dags_per_page)))