[Chore] Cleanup guided namespace, move to structured outputs config (#22772)

Signed-off-by: Aaron Pham <contact@aarnphm.xyz>
Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>
Co-authored-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

vllm/v1/request.py

@@ -67,7 +67,7 @@ class Request:
             # Generative models.
             assert sampling_params.max_tokens is not None
             self.max_tokens = sampling_params.max_tokens
-            if sampling_params.guided_decoding is not None:
+            if sampling_params.structured_outputs is not None:
                 self.status = RequestStatus.WAITING_FOR_FSM
                 self.use_structured_output = True