change schema -> dataset_schema (#442)

# What does this PR do?

- `schema` should not a field w/ pydantic warnings
- change `schema` to `dataset_schema`

<img width="855" alt="image"
src="https://github.com/user-attachments/assets/47cb6bb9-4be0-46a5-8701-24d24e2eaabd">


## Test Plan

```
pytest -v -s -m meta_reference_eval_together_inference_huggingface_datasetio eval/test_eval.py
```


## Before submitting

- [ ] This PR fixes a typo or improves the docs (you can dismiss the
other checks if that's the case).
- [ ] Ran pre-commit to handle lint / formatting issues.
- [ ] Read the [contributor
guideline](https://github.com/meta-llama/llama-stack/blob/main/CONTRIBUTING.md),
      Pull Request section?
- [ ] Updated relevant documentation.
- [ ] Wrote necessary unit or integration tests.

llama_stack/providers/inline/scoring/basic/scoring.py

@@ -60,17 +60,17 @@ class BasicScoringImpl(Scoring, ScoringFunctionsProtocolPrivate):
 
     async def validate_scoring_input_dataset_schema(self, dataset_id: str) -> None:
         dataset_def = await self.datasets_api.get_dataset(dataset_id=dataset_id)
-        if not dataset_def.schema or len(dataset_def.schema) == 0:
+        if not dataset_def.dataset_schema or len(dataset_def.dataset_schema) == 0:
             raise ValueError(
                 f"Dataset {dataset_id} does not have a schema defined. Please define a schema for the dataset."
             )
 
         for required_column in ["generated_answer", "expected_answer", "input_query"]:
-            if required_column not in dataset_def.schema:
+            if required_column not in dataset_def.dataset_schema:
                 raise ValueError(
                     f"Dataset {dataset_id} does not have a '{required_column}' column."
                 )
-            if dataset_def.schema[required_column].type != "string":
+            if dataset_def.dataset_schema[required_column].type != "string":
                 raise ValueError(
                     f"Dataset {dataset_id} does not have a '{required_column}' column of type 'string'."
                 )