Support `enum.global_enum`

Feature

Mypy should support module-level constants defined by enum.global_enum.

Pitch

enum.global_enum adds an enum’s members to the global namespace. Mypy reports errors for any use of global constants defined that way. It would make enum_global much more usable if mypy recognized them as defined.

Example file:

import enum

@enum.global_enum
class Example(enum.Enum):
    X = enum.auto()

print(X)

Current behavior:

$ python3.11 global_enum.py
X
$ mypy global_enum.py
global_enum.py:7: error: Name "X" is not defined  [name-defined]
Found 1 error in 1 file (checked 1 source file)

Start by running the supplied global_enum.py example with Python and mypy, then trace how mypy handles enum decorators and module-level name binding. Add support for names exported by enum.global_enum and verify that the example no longer reports a name-defined error, with regression coverage for this case.