drop Python 3.7 support #1462

Job	Run time
Python 3.8 on win32	3m 43s
py312 on alpine	1m 6s
Python 3.13 on win32	2m 45s
Python 3.8 on macos-13	1m 1s
py312 on alpine:aarch64	1m 25s
Python 3.8 on win64	1m 36s
Python 3.8 on macos-latest	1m 3s
py312 on ubuntu-rolling:aarch64	47s
Python 3.13 on win64	2m 30s
Python 3.13 on macos-13	1m 20s
pep8,packaging on linux, Rust stable	1m 12s
Python 3.13 on macos-latest	31s
mypy on linux, Rust stable	44s
py38 on linux, Rust stable	32s
py39 on linux, Rust stable	38s
py310 on linux, Rust stable	33s
py311 on linux, Rust stable	33s
py312 on linux, Rust stable	38s
py313 on linux, Rust stable	43s
pypy3 on linux, Rust stable	51s
pypy3 on linux, Rust stable	56s
py313 on linux, Rust 1.64.0	2m 44s
py313 on linux, Rust beta	54s
py313 on linux, Rust nightly	53s
all-green	1s
	29m 39s

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