add the remaining encodings submodules (#13123)

stdlib/encodings/undefined.pyi

@@ -0,0 +1,20 @@
+import codecs
+from _typeshed import ReadableBuffer
+
+# These return types are just to match the base types. In reality, these always
+# raise an error.
+
+class Codec(codecs.Codec):
+    def encode(self, input: str, errors: str = "strict") -> tuple[bytes, int]: ...
+    def decode(self, input: ReadableBuffer, errors: str = "strict") -> tuple[str, int]: ...
+
+class IncrementalEncoder(codecs.IncrementalEncoder):
+    def encode(self, input: str, final: bool = False) -> bytes: ...
+
+class IncrementalDecoder(codecs.IncrementalDecoder):
+    def decode(self, input: ReadableBuffer, final: bool = False) -> str: ...
+
+class StreamWriter(Codec, codecs.StreamWriter): ...
+class StreamReader(Codec, codecs.StreamReader): ...
+
+def getregentry() -> codecs.CodecInfo: ...