Drop support for Python 3.8 #3582

Job	Run time
check-links	45s
document	45s
smoke (amaranth-lang/amaranth-boards)	25s
test (3.9)	2m 31s
smoke (amaranth-lang/amaranth-stdio)	33s
smoke (amaranth-lang/amaranth-soc)	30s
test (3.10)	2m 30s
test (3.11)	3m 2s
test (3.12)	3m 43s
test (3.13)	3m 8s
test (pypy-3.9)	7m 4s
test (pypy-3.10)	5m 51s
test (3.14-dev)	1m 35s
publish-docs	6s
publish-docs-dev	0s
required	1s
publish-package	38s
publish-schemas	9s
publish-release	0s
	33m 16s

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