feat(responses): add include parameter (#3115)

Well our Responses tests use it so we better include it in the API, no?

I discovered it because I want to make sure `llama-stack-client` can be
used always instead of `openai-python` as the client (we do want to be
_truly_ compatible.)

docs/_static/llama-stack-spec.yaml

@@ -6188,6 +6188,12 @@ components:
           type: array
           items:
             $ref: '#/components/schemas/OpenAIResponseInputTool'
+        include:
+          type: array
+          items:
+            type: string
+          description: >-
+            (Optional) Additional fields to include in the response.
         max_infer_iters:
           type: integer
       additionalProperties: false