Use asyncgen hooks to call aclose() #3823

Job	Run time
check-links	1m 3s
smoke (amaranth-lang/amaranth-stdio)	1m 0s
smoke (amaranth-lang/amaranth-soc)	59s
document	57s
test (3.10)	2m 4s
smoke (amaranth-lang/amaranth-boards)	45s
test (pypy-3.9)	4m 28s
test (3.12)	3m 20s
test (3.9)	2m 25s
test (pypy-3.11)	3m 51s
test (3.15-dev)	1m 53s
test (pypy-3.10)	4m 37s
test (3.11)	2m 35s
test (3.13)	2m 46s
test (3.14)	2m 30s
publish-docs	6s
publish-docs-dev	0s
required	4s
publish-schemas	7s
publish-package	12s
publish-release	0s
	35m 42s

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