Manage ragflow-sdk with poetry (#3115)

### What problem does this PR solve?

Manage ragflow-sdk with poetry
### Type of change

- [x] Refactoring

sdk/python/ragflow_sdk/__init__.py

@@ -0,0 +1,10 @@
+import importlib.metadata
+
+__version__ = importlib.metadata.version("ragflow_sdk")
+
+from .ragflow import RAGFlow
+from .modules.dataset import DataSet
+from .modules.chat import Chat
+from .modules.session import Session
+from .modules.document import Document
+from .modules.chunk import Chunk