Rename files upload/download endpoints

[nolan1999]

• Rename /downloads/path -> /files/path/download
• /files/path/url endpoint
• Similar endpoint naming in worker-facing API
• File upload user-facing: /files/config or data/id/path/upload and /files/config or data/id/path/url?
• File upload worker-facing: /jobs/job_id/files/path/upload and /jobs/job_id/files/path/url?\
• Rename /download/{path} to /download/{file_id}