### Description

The stable REST API seems to be missing the functionality to delete a DAG. 
This would mirror clicking the "Trash Can" on the UI (and could maybe eventually power it)

![image](https://user-images.githubusercontent.com/80706212/131702280-2a8d0d74-6388-4b84-84c1-efabdf640cde.png)


### Use case/motivation

_No response_

### Related issues

_No response_

### Are you willing to submit a PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

airflow/www/views.py
"""Set state to 'up_for_retry'"""
        self.set_task_instance_state(tis, State.UP_FOR_RETRY)
        self.update_redirect()
        return redirect(self.get_redirect())
class DagModelView(AirflowModelView):
    """View to show records from DAG table"""
    route_base = '/dagmodel'
    datamodel = AirflowModelView.CustomSQLAInterface(DagModel)  
    class_permission_name = permissions.RESOURCE_DAG
    method_permission_name = {
        'list': 'read',
        'show': 'read',
    }
    base_permissions = [
        permissions.ACTION_CAN_READ,
        permissions.ACTION_CAN_EDIT,
        permissions.ACTION_CAN_DELETE,
    ]
    list_columns = [
        'dag_id',
        'is_paused',
        'last_parsed_time',
        'last_expired',
        'scheduler_lock',
        'fileloc',
        'owners',
    ]
    formatters_columns = {'dag_id': wwwutils.dag_link}
    base_filters = [['dag_id', DagFilter, lambda: []]]
    def get_query(self):