feat(primitives): manually implement arbitrary for signature #1821

Job	Run time
feature-checks	3m 0s
miri --no-default-features	3m 22s
miri	3m 23s
clippy	43s
docs	24s
miri --all-features	4m 20s
fmt	10s
wasm	26s
test ubuntu-latest stable --no-default-features	54s
test ubuntu-latest stable	1m 8s
test ubuntu-latest beta --no-default-features	46s
test ubuntu-latest beta	45s
test ubuntu-latest nightly --no-default-features	50s
test ubuntu-latest nightly	45s
test ubuntu-latest 1.65 --no-default-features	1m 4s
test ubuntu-latest 1.65	1m 13s
test windows-latest stable --no-default-features	2m 2s
test windows-latest stable	2m 9s
test windows-latest beta --no-default-features	1m 56s
test windows-latest beta	2m 18s
test windows-latest nightly --no-default-features	1m 37s
test windows-latest nightly	1m 37s
test windows-latest 1.65 --no-default-features	2m 2s
test windows-latest 1.65	1m 51s
test ubuntu-latest 1.65 --features json	1m 9s
test windows-latest 1.65 --features json	1m 46s
test ubuntu-latest stable --all-features	1m 22s
test ubuntu-latest beta --all-features	1m 9s
test ubuntu-latest nightly --all-features	1m 6s
	45m 17s

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