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.

"""Duration calculation."""
        end_date = self.get("end_date")
        start_date = self.get("start_date")
        difference = "0s"
        if start_date and end_date:
            difference = td_format(end_date - start_date)
        return difference
    formatters_columns = {
        "execution_date": wwwutils.datetime_f("execution_date"),
        "state": wwwutils.state_f,
        "start_date": wwwutils.datetime_f("start_date"),
        "end_date": wwwutils.datetime_f("end_date"),
        "queued_at": wwwutils.datetime_f("queued_at"),
        "dag_id": wwwutils.dag_link,
        "run_id": wwwutils.dag_run_link,
        "conf": wwwutils.json_f("conf"),
        "duration": duration_f,
    }
    @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: list[DagRun]):