Switch from tox to nox #1259

Job	Run time
tests-cryptography-main on ubuntu-rolling	1m 52s
Downstream tests for certbot	59s
Downstream tests for twisted	1m 47s
Downstream tests for certbot-josepy	30s
linux (3.8, tests)	1m 13s
linux (3.12, tests)	1m 46s
linux (3.7, tests)	1m 45s
linux (pypy-3.9, tests)	1m 32s
linux (3.9, tests)	1m 21s
linux (3.13-dev, tests)	1m 14s
linux (3.11, tests)	1m 2s
linux (3.10, tests)	1m 13s
linux (pypy-3.10, tests)	1m 29s
linux (3.9, tests-cryptography-minimum)	1m 13s
linux (3.12, tests-cryptography-main)	1m 58s
linux (3.8, tests-cryptography-main)	2m 5s
linux (3.11, tests-cryptography-main)	2m 1s
linux (3.11, tests-wheel, windows-2022)	44s
linux (3.9, tests-cryptography-main)	2m 12s
linux (3.11, tests-cryptography-minimum)	1m 11s
linux (3.12, tests-cryptography-minimum)	1m 12s
linux (3.10, tests-cryptography-minimum)	1m 18s
linux (3.7, tests-cryptography-minimum)	1m 21s
linux (3.13-dev, tests-cryptography-main)	1m 48s
linux (3.8, tests-cryptography-minimum)	1m 9s
linux (3.13-dev, tests-cryptography-minimum)	1m 17s
linux (3.9, docs)	23s
linux (3.13, mypy)	20s
linux (3.9, tests-cryptography-minimum-wheel)	29s
linux (3.11, lint)	11s
linux (3.10, tests-cryptography-main)	1m 45s
linux (pypy-3.10, tests-cryptography-main)	2m 18s
linux (3.9, tests-random-order)	1m 12s
linux (3.9, check-manifest)	13s
linux (pypy-3.10, tests-cryptography-minimum)	1m 39s
linux (3.9, tests-wheel)	28s
linux (pypy-3.9, tests-cryptography-main)	2m 8s
all-green	14s
	48m 32s

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