enum: More changes for 3.11

[AlexWaygood]

In 3.11+, enum.Flags are iterable and sized:

C:\Users\alexw\coding\cpython>python
Running Debug|x64 interpreter...
Python 3.12.0a0 (main, May 17 2022, 16:54:26) [MSC v.1931 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from enum import *
>>> class Foo(Flag):
...     X = 1
...     Y = 2
...     Z = X | Y
...
>>> len(Foo.X)
1
>>> len(Foo.Z)
2
>>> list(Foo.X)
[<Foo.X: 1>]
>>> list(Foo.Z)
[<Foo.X: 1>, <Foo.Y: 2>]

CPython changes:

• bpo-38250: [Enum] single-bit flags are canonical cpython#24215
• bpo-32218: make Flag and IntFlag members iterable cpython#22221
• bpo-34750: [Enum] add _EnumDict.update() support cpython#23725

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉