API: Fix blocking iterator execution

Run these iterators on the background thread. On startup, the API
spawns a background thread as needed to run sync code on without blocking
the event loop.

Use asyncio's run_thread function since it allows for errors to be
propegated.

Signed-off-by: kingbri <bdashore3@proton.me>

endpoints/OAI/utils/completion.py

@@ -1,7 +1,7 @@
 """Completion utilities for OAI server."""
 
-from asyncio import CancelledError
 import pathlib
+from asyncio import CancelledError
 from fastapi import HTTPException
 from typing import Optional