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.

_add_columns = _edit_columns = [
        "conn_id",
        "conn_type",
        "description",
        "host",
        "schema",
        "login",
        "password",
        "port",
        "extra",
    ]
    
    
    add_form = edit_form = ConnectionFormProxy
    add_template = "airflow/conn_create.html"
    edit_template = "airflow/conn_edit.html"
    add_widget = ConnectionFormWidget
    edit_widget = ConnectionFormWidget
    base_order = ("conn_id", "asc")
    def _iter_extra_field_names(self) -> Iterator[tuple[str, str]]:
        """Iterate through provider-backed connection fields.
        Note that this cannot be a property (including a cached property)
        because Flask-Appbuilder attempts to access all members on startup, and
        using a property would initialize the providers manager too eagerly.
        """
        return ((k, v.field_name) for k, v in ProvidersManager().connection_form_widgets.items())
    @property
    def add_columns(self) -> list[str]: