fix: improve `extension!` macro #3249

Job	Run time
compute-jobs	9s
build-linux / linux coverage	3m 5s
build-linux / linux lint-deps	2m 8s
build-linux / linux lint	54s
build-linux / linux test-ops	5m 57s
build-linux / linux test-publish	1m 35s
build-linux / linux test-miri	5m 54s
build-linux / linux test	3m 7s
build-linux-arm / linux-arm test	4m 41s
build-linux-arm / linux-arm test-miri	10m 23s
build-linux-arm / linux-arm lint	1m 24s
build-linux-xl / linux-xl test-valgrind	19m 33s
build-macos / macos test	2m 33s
build-macos / macos lint	56s
build-windows / windows lint	3m 16s
build-windows / windows test	6m 30s
success	1s
	1h 12m 6s

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