refactor: The first refactored version for sdk release (#907)

Co-authored-by: chengfangyin2 <chengfangyin3@jd.com>

dbgpt/__init__.py

@@ -0,0 +1,17 @@
+from dbgpt.component import SystemApp, BaseComponent
+
+
+__ALL__ = ["SystemApp", "BaseComponent"]
+
+_CORE_LIBS = ["core", "rag", "model", "agent", "datasource", "vis", "storage", "train"]
+_SERVE_LIBS = ["serve"]
+_LIBS = _CORE_LIBS + _SERVE_LIBS
+
+
+def __getattr__(name: str):
+    # Lazy load
+    import importlib
+
+    if name in _LIBS:
+        return importlib.import_module("." + name, __name__)
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")