Refactor code to extract class name from custom code

- Updatethe `get_function_custom` function to use the `validate.extract_class_name` function to extract class name from the `code` parameter.
- Modify `instantiate_tool` function to update the `class_object` with the return value of `get_function_custom` and call the `build` method on the instantiated object with the remaining params.
- Add a new function `extract_class_name` in the `validate` module to extract class name from the `code` parameter.

src/backend/langflow/interface/initialize/loading.py

@@ -178,8 +178,8 @@ def instantiate_tool(node_type, class_object, params):
         params["func"] = get_function(params.get("code"))
         return class_object(**params)
     elif node_type == "CustomComponent":
-        params["func"] = get_function_custom(params.get("code"))
-        return class_object(**params)
+        class_object = get_function_custom(params.pop("code"))
+        return class_object().build(**params)
     # For backward compatibility
     elif node_type == "PythonFunction":
         function_string = params["code"]