cmov: add proptests #103

Job	Run time
test-careful	58s
test-miri (x86_64-unknown-linux-gnu)	40s
test-miri (s390x-unknown-linux-gnu)	1m 1s
test (1.85.0)	20s
build (stable, thumbv7em-none-eabi)	15s
build (1.85.0, wasm32-unknown-unknown)	15s
minimal-versions / minimal-versions	22s
test (stable)	10s
build (stable, wasm32-unknown-unknown)	12s
build (1.85.0, thumbv7em-none-eabi)	15s
	4m 28s

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