[HttpFoundation] Added a switch to delete file after the response is send

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | N/A
| License       | MIT
| Doc PR        | symfony/symfony-docs#3975

I have not done any Unit Tests for this code as I suspect there may already be a way to solve my problem of deleting a file after the request was sent. Is it possible to use `sendContent` and delete the file after that? My attempts were unsuccessful.

If this code is desirable, please assist me in how I would write an unit test for this. Thanks.

TODO:
- [x] Add unit tests
- [x] Update documentation
- [x] Mention that using `X-Sendfile` will overwrite deleteFileAfterSend
Shouldn't this be set already in variable declaration?
```php
protected $deleteFileAfterSend = false;