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.

task_ids_or_regex=task_ids_or_regex,
            include_downstream=downstream,
            include_upstream=upstream,
        )
        if len(dag.task_dict) > 1:
            
            task_ids.extend(tid for tid in dag.task_dict if tid != task_id)
        response = self._clear_dag_tis(
            dag,
            start_date,
            end_date,
            origin=origin,
            task_ids=task_ids,
            recursive=recursive,
            confirmed=confirmed,
            only_failed=only_failed,
            session=session,
        )
        del locked_dag_run_ids
        return response
    @expose("/dagrun_clear", methods=["POST"])
    @auth.has_access(
        [
            (permissions.ACTION_CAN_EDIT, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_DELETE, permissions.RESOURCE_TASK_INSTANCE),
        ]
    )
    @action_logging
    @provide_session
    def dagrun_clear(self, *, session: Session = NEW_SESSION):