fix(api): allow original image detail in Chat Completions (#4005)

## Summary

Allow original as an image detail value in Chat Completions requests.

## Changes

- Add original to the accepted image_url.detail values for Chat
Completions. Existing values and the auto default are unchanged.

Co-authored-by: marcuswood-oai <323319819+marcuswood-oai@users.noreply.github.com>