### 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
]
    order_columns = [
        item for item in list_columns if item not in ['try_number', 'log_url', 'external_executor_id']
    ]
    search_columns = [
        'state',
        'dag_id',
        'task_id',
        'execution_date',
        'hostname',
        'queue',
        'pool',
        'operator',
        'start_date',
        'end_date',
        'queued_dttm',
    ]
    edit_columns = [
        'state',
        'dag_id',
        'task_id',
        'execution_date',
        'start_date',
        'end_date',
    ]
    add_exclude_columns = ["next_method", "next_kwargs", "trigger_id"]
    edit_form = TaskInstanceEditForm
    base_order = ('job_id', 'asc')
    base_filters = [['dag_id', DagFilter, lambda: []]]
    def log_url_formatter(self):