Since we use [`DEFAULT_PROTOCOL=2`](https://github.com/pytorch/pytorch/blob/main/torch/serialization.py#L62), some functions/classes that were renamed from python 2-->3 will be pickled with their python2 name. This PR ensures that when a mod `GLOBAL <python2_mod>.<python2_name> ` is encountered, [following the strategy used by pickle](https://github.com/python/cpython/blob/main/Lib/pickle.py#L1590C13-L1593C63) it is properly mapped to `<python3_mod>.<python3_name>`.

This fix ensures that `add_safe_globals` works properly for such functions/classes (i.e. users will allowlist the python3 func and the weights_only unpickler will do the appropriate translation when checking whether a class was allowlisted).

An example is as follows:
`__builtin__` was named to `builtins`, see the [release notes for Python 3.0](https://docs.python.org/3/whatsnew/3.0.html)

> Renamed module `__builtin__` to [`builtins`](https://docs.python.org/3/library/builtins.html#module-builtins) (removing the underscores, adding an ‘s’). The __builtins__ variable found in most global namespaces is unchanged. To modify a builtin, you should use [builtins](https://docs.python.org/3/library/builtins.html#module-builtins), not `__builtins__`!

However, since we use [`DEFAULT_PROTOCOL=2`](https://github.com/pytorch/pytorch/blob/main/torch/serialization.py#L62), builtins will be pickled with their module string as `__builtin__`.

```python
>>> import pickle
>>> import pickletools
>>> print.__module__
'builtins'
>>> with open('print.pkl', 'wb') as f:
>>>      pickle.dump(print, f, protocol=2) # 2 because this is the default protocol used by pytorch
>>> with open('print.pkl', 'rb') as f:
>>>     pickletools.dis(f)
0: \x80 PROTO      2
2: c    GLOBAL     '__builtin__ print' # pickle saves the module string as __builtin__ !!! :(
21: q    BINPUT     0
23: .    STOP
```

Pull Request resolved: pytorch#129244
Approved by: https://github.com/albanD