Add back module-level __getattr__ to encodings (#5261)

This is needed for submodules, such as `encodings.cp437`.

stdlib/encodings/__init__.pyi

@@ -1,7 +1,10 @@
 from codecs import CodecInfo
-from typing import Optional, Union
+from typing import Any, Optional, Union
 
 class CodecRegistryError(LookupError, SystemError): ...
 
 def normalize_encoding(encoding: Union[str, bytes]) -> str: ...
 def search_function(encoding: str) -> Optional[CodecInfo]: ...
+
+# Needed for submodules
+def __getattr__(name: str) -> Any: ...  # incomplete