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.

dag_contents_template = "from airflow import DAG\ndag = DAG('{}', tags=['{}'])"
    dag_contents_template_with_read_perm = (
        "from airflow import DAG\ndag = DAG('{}', tags=['{}'], "
        "access_control={{'role_single_dag':{{'can_edit'}}}}) "
    )
    with create_session() as session:
        for dag_id, tag in list(zip(TEST_FILTER_DAG_IDS, TEST_TAGS)):
            filename = os.path.join(tmpdir, f"{dag_id}.py")
            if dag_id == "filter_test_1":
                with open(filename, "w") as f:
                    f.writelines(dag_contents_template_with_read_perm.format(dag_id, tag))
            else:
                with open(filename, "w") as f:
                    f.writelines(dag_contents_template.format(dag_id, tag))
            _process_file(filename, session)
@pytest.fixture()
def broken_dags(tmpdir, working_dags):