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

Bắt đầu bằng việc xem xét pull request được liên kết gh-127766 và các thay đổi được đề xuất trong issue đối với ctypes.DllGetClassObject và DllCanUnloadNow. Truy vết các hook ctypes hiện có và phần tích hợp với comtypes.server.inprocserver được mô tả ở đây; công việc được xem là hoàn tất khi API và hành vi deprecation đã được thống nhất, được triển khai mà không gây ra lỗi ngoài ý muốn trong comtypes và được các bài kiểm thử liên quan bao phủ.