Implement --at-least-one-of #2516

Job	Run time
miri	1m 7s
test (1.26)	6m 43s
test (1.30)	6m 44s
test (1.31)	6m 39s
test (1.36)	6m 41s
test (1.39)	6m 42s
test (1.41)	6m 40s
test (stable)	6m 43s
test (beta)	6m 37s
test (nightly)	6m 42s
test (nightly, macos-11)	6m 38s
test (nightly, windows-2019)	3m 14s
build (aarch64-unknown-linux-gnu)	1m 45s
build (aarch64-unknown-linux-musl)	1m 24s
build (aarch64-apple-darwin)	1m 51s
build (aarch64-pc-windows-msvc)	3m 50s
build (x86_64-unknown-linux-gnu)	1m 23s
build (x86_64-unknown-linux-musl)	1m 19s
build (x86_64-apple-darwin)	1m 59s
build (x86_64-pc-windows-msvc)	3m 21s
build (x86_64-unknown-freebsd)	1m 56s
deny / deny	22s
msrv / msrv	2m 56s
tidy / tidy	1m 9s
	1h 34m 25s

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