unregister api for dataset

Test Plan:

**Type checker and check that the build compiles**

**Unit Tests**

**E2E Tests**

// Screenshots and videos
| Before | After |
|--|
| … | … |

llama_stack/providers/datatypes.py

@@ -63,6 +63,8 @@ class MemoryBanksProtocolPrivate(Protocol):
 class DatasetsProtocolPrivate(Protocol):
     async def register_dataset(self, dataset: Dataset) -> None: ...
 
+    async def unregister_dataset(self, dataset_id: str) -> None: ...
+
 
 class ScoringFunctionsProtocolPrivate(Protocol):
     async def list_scoring_functions(self) -> List[ScoringFn]: ...

llama_stack/providers/inline/datasetio/localfs/datasetio.py

@@ -97,6 +97,9 @@ class LocalFSDatasetIOImpl(DatasetIO, DatasetsProtocolPrivate):
             dataset_impl=dataset_impl,
         )
 
+    async def unregister_dataset(self, dataset_id: str) -> None:
+        del self.dataset_infos[dataset_id]
+
     async def get_rows_paginated(
         self,
         dataset_id: str,

llama_stack/providers/remote/datasetio/huggingface/huggingface.py

@@ -63,6 +63,11 @@ class HuggingfaceDatasetIOImpl(DatasetIO, DatasetsProtocolPrivate):
         )
         self.dataset_infos[dataset_def.identifier] = dataset_def
 
+    async def unregister_dataset(self, dataset_id: str) -> None:
+        key = f"{DATASETS_PREFIX}{dataset_id}"
+        await self.kvstore.delete(key=key)
+        del self.dataset_infos[dataset_id]
+
     async def get_rows_paginated(
         self,
         dataset_id: str,

llama_stack/providers/tests/datasetio/test_datasetio.py

@@ -81,6 +81,18 @@ class TestDatasetIO:
         assert len(response) == 1
         assert response[0].identifier == "test_dataset"
 
+        with pytest.raises(Exception) as exc_info:
+            # unregister a dataset that does not exist
+            await datasets_impl.unregister_dataset("test_dataset2")
+
+        await datasets_impl.unregister_dataset("test_dataset")
+        response = await datasets_impl.list_datasets()
+        assert isinstance(response, list)
+        assert len(response) == 0
+
+        with pytest.raises(Exception) as exc_info:
+            await datasets_impl.unregister_dataset("test_dataset")
+
     @pytest.mark.asyncio
     async def test_get_rows_paginated(self, datasetio_stack):
         datasetio_impl, datasets_impl = datasetio_stack