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.

permissions.ACTION_CAN_ACCESS_MENU,
    ]
    list_columns = [
        "id",
        "dag_id",
        "run_id",
        "dag_run.execution_date",
        "task_id",
        "map_index",
        "try_number",
        "start_date",
        "end_date",
        "duration",
        "reschedule_date",
    ]
    label_columns = {
        "dag_run.execution_date": "Logical Date",
    }
    search_columns = [
        "dag_id",
        "task_id",
        "run_id",
        "execution_date",
        "start_date",
        "end_date",
        "reschedule_date",
    ]
    base_order = ("id", "desc")
    base_filters = [["dag_id", DagFilter, lambda: []]]
    def duration_f(self):