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.

"clear",
        lazy_gettext("Clear"),
        lazy_gettext(
            "Are you sure you want to clear the state of the selected task"
            " instance(s) and set their dagruns to the QUEUED state?"
        ),
        single=False,
    )
    @action_has_dag_edit_access
    @provide_session
    @action_logging
    def action_clear(self, task_instances, session: Session = NEW_SESSION):
        """Clears the action."""
        try:
            dag_to_tis = collections.defaultdict(list)
            for ti in task_instances:
                dag = get_airflow_app().dag_bag.get_dag(ti.dag_id)
                dag_to_tis[dag].append(ti)
            for dag, task_instances_list in dag_to_tis.items():
                models.clear_task_instances(task_instances_list, session, dag=dag)
            session.commit()
            flash(f"{len(task_instances)} task instances have been cleared")
        except Exception as e:
            flash(f'Failed to clear task instances: "{e}"', "error")
        self.update_redirect()
        return redirect(self.get_redirect())
    @action("muldelete", "Delete", "Are you sure you want to delete selected records?", single=False)
    @action_has_dag_edit_access
    @action_logging
    def action_muldelete(self, items):