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.

upstream: bool,
        downstream: bool,
        future: bool,
        past: bool,
        state: TaskInstanceState,
    ):
        dag: DAG = get_airflow_app().dag_bag.get_dag(dag_id)
        if not run_id:
            flash(f"Cannot mark tasks as {state}, as DAG {dag_id} has never run", "error")
            return redirect(origin)
        altered = dag.set_task_group_state(
            group_id=group_id,
            run_id=run_id,
            state=state,
            upstream=upstream,
            downstream=downstream,
            future=future,
            past=past,
        )
        flash(f"Marked {state} on {len(altered)} task instances")
        return redirect(origin)
    @expose("/confirm", methods=["GET"])
    @auth.has_access(
        [
            (permissions.ACTION_CAN_EDIT, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_EDIT, permissions.RESOURCE_TASK_INSTANCE),
        ]
    )
    @action_logging
    def confirm(self):