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.

sorting_direction=arg_sorting_direction if arg_sorting_direction else None,
            ),
            num_runs=num_runs,
            tags=tags,
            owner_links=owner_links_dict,
            state_color=state_color_mapping,
            status_filter=arg_status_filter,
            status_count_all=all_dags_count,
            status_count_active=status_count_active,
            status_count_paused=status_count_paused,
            tags_filter=arg_tags_filter,
            sorting_key=arg_sorting_key,
            sorting_direction=arg_sorting_direction,
            auto_refresh_interval=conf.getint("webserver", "auto_refresh_interval"),
            dataset_triggered_next_run_info=dataset_triggered_next_run_info,
        )
    @expose("/datasets")
    @auth.has_access([(permissions.ACTION_CAN_READ, permissions.RESOURCE_DATASET)])
    def datasets(self):
        """Datasets view."""
        state_color_mapping = State.state_color.copy()
        state_color_mapping["null"] = state_color_mapping.pop(None)
        return self.render_template(
            "airflow/datasets.html",
            state_color_mapping=state_color_mapping,
        )
    @expose("/next_run_datasets_summary", methods=["POST"])
    @auth.has_access([(permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG)])
    @provide_session
    def next_run_datasets_summary(self, session: Session = NEW_SESSION):