Replace ctypes.DllGetClassObject and remove DllCanUnloadNow

As far as I can tell, these functions are hooks: third-party code is meant to replace them.

Their implementation in ctypes (i.e. their default behaviour) is to import and call the same-named functions from a third-party library, comtypes.server.inprocserver. This is not good. comtypes should instead register their hook on import.

Here's a possible plan to make the API boundary better without breaking users.

DllCanUnloadNow

While the Python interpreter is running, it is not safe to unload the shared library that contains _ctypes. Therefore:

• The C function DllCanUnloadNow exported from _ctypes should be changed to always return S_FALSE. We should change that now, without a deprecation period. (Note that the comtypes hook already does this.)
• We should stop importing and calling comtypes.server.inprocserver. I'm not sure about the necessary deprecation period, but I think that it should be a non-breaking change and can also be done immediately. Or is someone relying on it for side effects? O_o
• Setting and getting the hook should be deprecated. In about Python 3.18 we should stop calling it, and remove it.

DllGetClassObject

This one, on the other hand, sounds like a useful hook. It also looks like an inprocess COM server need a special build so it's not useful to allow multiple hooks -- replacing a global one is enough. Is that so?
If yes:

• ctypes.DllGetClassObject (the default implementation) should raise a DeprecationWarning. In about Python 3.18, it should be changed to do nothing, just, return CLASS_E_CLASSNOTAVAILABLE.
• comtypes should be changed: on import, it should replace ctypes.DllGetClassObject with its own hook.

This should ensure that old versions of comtypes still work as before (until after the deprecation period).

Does that sound reasonable?
cc @junkmd

Linked PRs

• gh-127766

Commencez par examiner la pull request liée gh-127766 et les modifications proposées dans l’issue pour ctypes.DllGetClassObject et DllCanUnloadNow. Suivez les hooks existants de ctypes ainsi que l’intégration de comtypes.server.inprocserver décrite ici ; le travail sera considéré comme terminé lorsque l’API et le comportement de dépréciation auront été convenus, que l’implémentation n’aura pas entraîné de régression involontaire de comtypes et qu’elle sera couverte par les tests pertinents.