feat(dataset api): (1.5/n) fix dataset registeration (#1659)

# What does this PR do?

- fix dataset registeration & iterrows
> NOTE: the URL endpoint is changed to datasetio due to flaky path
routing

[//]: # (If resolving an issue, uncomment and update the line below)
[//]: # (Closes #[issue-number])

## Test Plan
```
LLAMA_STACK_CONFIG=fireworks pytest -v tests/integration/datasets/test_datasets.py
```
<img width="854" alt="image"
src="https://github.com/user-attachments/assets/0168b352-1c5a-48d1-8e9a-93141d418e54"
/>


[//]: # (## Documentation)

docs/openapi_generator/pyopenapi/generator.py

@@ -552,8 +552,8 @@ class Generator:
             print(op.defining_class.__name__)
 
         # TODO (xiyan): temporary fix for datasetio inner impl + datasets api
-        if op.defining_class.__name__ in ["DatasetIO"]:
-            op.defining_class.__name__ = "Datasets"
+        # if op.defining_class.__name__ in ["DatasetIO"]:
+        #     op.defining_class.__name__ = "Datasets"
 
         doc_string = parse_type(op.func_ref)
         doc_params = dict(