drop python 3.7, fix 3.12 builds #299

Job	Run time
test py3.8	51s
test py3.9	1m 0s
lint	26s
test py3.10	49s
test py3.11	57s
build os=linux target=x86_64 int=all ml=musllinux_1_1	1m 46s
build os=linux target=aarch64 int=all ml=musllinux_1_1	1m 42s
test py3.12	52s
build os=macos target=x86_64 int=all ml=auto	3m 33s
build os=macos target=aarch64 int=all ml=auto	2m 35s
build os=windows target=x86_64 int=all ml=auto	3m 9s
build os=windows target=aarch64 int=3.11 3.12 ml=auto	3m 24s
build os=linux target=i686 int=all ml=auto	2m 51s
build os=linux target=armv7 int=all ml=auto	2m 24s
build os=linux target=ppc64le int=all ml=auto	2m 16s
build os=linux target=s390x int=all ml=auto	3m 2s
build os=windows target=i686 int=all ml=auto	3m 47s
check	2s
inspect-pypi-assets	0s
release	0s
	35m 26s

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