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

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

pyrightconfig.json

@@ -6,6 +6,7 @@
     ],
     "exclude": [
         "**/@python2",
+        "stdlib/encodings",
         "stdlib/sqlite3/dbapi2.pyi",
         "stdlib/tkinter",
         "stdlib/xml/dom",
@@ -83,4 +84,4 @@
     // Mypy's overlapping overload logic misses these issues (see mypy
     // issue #10143 and #10157).
     "reportOverlappingOverload": "none"
-}
+}