ctutils: additional `u64` constructors for `Choice` #47

Job	Run time
test (1.85.0)	16s
test (stable)	21s
build (stable, thumbv7em-none-eabi)	13s
build (1.85.0, thumbv7em-none-eabi)	18s
test-careful	53s
minimal-versions / minimal-versions	26s
build (1.85.0, wasm32-unknown-unknown)	16s
build (stable, wasm32-unknown-unknown)	10s
	2m 53s

Provide feedback