Rework test_ctypes

[vstinner]

The ctypes module was first maintained outside Python, then moved into Python stdlib. Its test suite wasn't cleaned recently. I create this issue to track work on this topic.

Linked PRs

• gh-105751: test_ctypes gets Windows attrs from ctypes #105758
• gh-105751: test_ctypes.test_numbers uses top level imports #105762
• gh-105751: test_ctypes avoids "from ctypes import *" #105768
• gh-105751: test_ctypes avoids the operator module #105797
• gh-105751: test_ctypes: Remove @need_symbol decorator #105798
• gh-105751: Cleanup test_ctypes imports #105803
• gh-105751: Remove dead code in test_ctypes #105814
• gh-105751: Remove dead code in test_ctypes #105817
• gh-105751: Reenable disable test_ctypes tests #105818
• gh-105751: Remove platform usage in test_ctypes #105819
• gh-105751, test_ctypes: Remove disabled tests #105826
• [3.12] gh-105751, test_ctypes: Remove disabled tests (GH-105826) #107483
• [3.11] gh-105751, test_ctypes: Remove disabled tests (GH-105826) #107484
• gh-105751: Remove obsolete object base class in some ctypes tests #107460
• [3.12] gh-105751: Remove obsolete object base class in some ctypes tests (GH-107460) #107501
• [3.11] gh-105751: Remove obsolete object base class in some ctypes tests (GH-107460) #107502