Delete and edit files that have been uploaded to tests/engagements through API

[andrew-myer]

After a file is uploaded to a test or engagement through the POST /api/v2/tests/{id}/files/ or POST /api/v2/engagements/{id}/files/ API endpoints, the only way to delete or edit the file is through the UI. It would be helpful to have the ability to edit and delete files in the API as well.

Ideally the function to delete and edit files would be available in the API endpoints
PATCH,DELETE /api/v2/tests/{id}/files/{file_id}
PATCH,DELETE /api/v2/engagements/{id}/files/{file_id}