Add support for Python 3.12 #431

Job	Run time
Python 3.6 on macOS	4m 51s
Python 3.6 on Windows x86	4m 20s
Python 3.12 on macOS	5m 1s
Python 3.7 on Windows x86	3m 35s
Python 3.12 (minimal build) on macOS	5m 10s
Python 3.8 on Windows x86	3m 15s
Linux docs	2m 5s
Python 3.9 on Windows x86	4m 11s
Linux meta	2m 37s
Python 3.10 on Windows x86	3m 16s
Linux mypy	1m 51s
Python 3.11 on Windows x86	4m 9s
Linux pypy3	5m 0s
Python 3.12 on Windows x86	4m 47s
Linux pypy3	3m 53s
Python 3.6 on Windows x64	4m 47s
Linux py36	2m 8s
Python 3.7 on Windows x64	3m 42s
Linux py37	2m 1s
Python 3.8 on Windows x64	2m 59s
Linux py38	2m 17s
Python 3.9 on Windows x64	3m 1s
Linux py39	1m 56s
Python 3.10 on Windows x64	3m 4s
Linux py310	2m 20s
Python 3.11 on Windows x64	4m 14s
Linux py311	1m 59s
Linux py312	2m 34s
Python 3.12 on Windows x64	4m 26s
Linux py312 system	3m 12s
Linux py312 minimal	2m 2s
	1h 44m 43s

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