### 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
if not task_instance:
                return None
            
            
            
            task_instance_data = [
                task_instance.state,
                task_instance.try_number,
                None,  
                None,  
            ]
            if task_instance.start_date:
                
                task_instance_data[2] = int(task_instance.start_date.timestamp())
                if task_instance.duration is not None:
                    task_instance_data[3] = truncate_task_duration(task_instance.duration)
            return task_instance_data
        def recurse_nodes(task, visited):