AF_DECnet is missing from socket.AddressFamily

Bug report

Bug description:

This code populates the AddressFamily enum:

IntEnum._convert_(
        'AddressFamily',
        __name__,
        lambda C: C.isupper() and C.startswith('AF_'))

But AF_DECnet isn't all uppercase so it's currently excluded. Do we need the isupper() test? I don't see anything that begins with AF_ in socket other than the existing members of AddressFamily and AF_DECnet.

CPython versions tested on:

3.13

Operating systems tested on:

macOS

Linked PRs

• gh-127548

從 socket 模組開始，該模組中的 AddressFamily 由 IntEnum.convert() 填充，並檢查 AF_* 名稱，尤其是 AF_DECnet。查看連結的 PR gh-127548 和現有的 socket 測試；完成的標準是 AF_DECnet 在 socket.AddressFamily 中獲得表示，且不會導致其他位址族成員發生回歸。