ctutils: use new `cmov` trait impls; remove `unsafe` #1201

Job	Run time
test-derive (stable)	24s
x86 (x86_64-unknown-linux-gnu, stable)	13s
test-derive (1.85.0)	28s
x86 (x86_64-unknown-linux-gnu, 1.85.0)	24s
cross (powerpc-unknown-linux-gnu, 1.85.0)	45s
cross (aarch64-unknown-linux-gnu, stable)	52s
cross (powerpc-unknown-linux-gnu, stable)	42s
build (1.85.0, thumbv7em-none-eabi)	16s
build (1.85.0, wasm32-unknown-unknown)	18s
build (stable, thumbv7em-none-eabi)	13s
cross (aarch64-unknown-linux-gnu, 1.85.0)	43s
build (stable, armv7a-none-eabi)	12s
build (stable, wasm32-unknown-unknown)	8s
build (1.85.0, armv7a-none-eabi)	18s
test (x86_64-apple-darwin, macos-latest, 1.85.0)	22s
test (x86_64-pc-windows-msvc, windows-latest, 1.85.0)	37s
test (x86_64-pc-windows-msvc, windows-latest, stable)	2m 11s
test (x86_64-unknown-linux-gnu, ubuntu-latest, stable)	12s
test (x86_64-apple-darwin, macos-latest, stable)	21s
test (x86_64-unknown-linux-gnu, ubuntu-latest, 1.85.0)	15s
minimal-versions / minimal-versions	59s
test (i686-unknown-linux-gnu, ubuntu-latest, 1.85.0, sudo apt update && sudo apt install gcc-mult...	37s
test (i686-unknown-linux-gnu, ubuntu-latest, stable, sudo apt update && sudo apt install gcc-mult...	32s
	12m 2s

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