create list_dataset api and tests (#1138)

### What problem does this PR solve?

This PR have completed both HTTP API and Python SDK for 'list_dataset".
In addition, there are tests for it.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

sdk/python/ragflow/dataset.py

@@ -18,4 +18,4 @@ class DataSet:
         self.user_key = user_key
         self.dataset_url = dataset_url
         self.uuid = uuid
-        self.name = name
+        self.name = name