Rename ipython to tool (#756)

See https://github.com/meta-llama/llama-models/pull/261 for the
corresponding PR in llama-models.

Once these PRs land, you need to work `main` from llama-models (vs. from
pypi)

llama_stack/providers/remote/inference/nvidia/openai_utils.py

@@ -144,7 +144,7 @@ def _convert_message(message: Message | Dict) -> OpenAIChatCompletionMessage:
             message = UserMessage(**message)
         elif message["role"] == "assistant":
             message = CompletionMessage(**message)
-        elif message["role"] == "ipython":
+        elif message["role"] == "tool":
             message = ToolResponseMessage(**message)
         elif message["role"] == "system":
             message = SystemMessage(**message)