bpo-38659: [Enum] add _simple_enum decorator (GH-25285)

add:

_simple_enum decorator to transform a normal class into an enum
_test_simple_enum function to compare
_old_convert_ to enable checking _convert_ generated enums
_simple_enum takes a normal class and converts it into an enum:

@simple_enum(Enum)
class Color:
    RED = 1
    GREEN = 2
    BLUE = 3

_old_convert_ works much like _convert_ does, using the original logic:

# in a test file
import socket, enum
CheckedAddressFamily = enum._old_convert_(
        enum.IntEnum, 'AddressFamily', 'socket',
        lambda C: C.isupper() and C.startswith('AF_'),
        source=_socket,
        )

test_simple_enum takes a traditional enum and a simple enum and
compares the two:

# in the REPL or the same module as Color
class CheckedColor(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3

_test_simple_enum(CheckedColor, Color)

_test_simple_enum(CheckedAddressFamily, socket.AddressFamily)

Any important differences will raise a TypeError

Lib/uuid.py

@@ -47,7 +47,7 @@ Typical usage:
 import os
 import sys
 
-from enum import Enum
+from enum import Enum, _simple_enum
 
 
 __author__ = 'Ka-Ping Yee <ping@zesty.ca>'
@@ -75,7 +75,8 @@ int_ = int      # The built-in int type
 bytes_ = bytes  # The built-in bytes type
 
 
-class SafeUUID(Enum):
+@_simple_enum(Enum)
+class SafeUUID:
     safe = 0
     unsafe = -1
     unknown = None