ctutils: add `u128` methods to `Choice` (#1277) #63

Job	Run time
test (stable)	15s
test-miri (s390x-unknown-linux-gnu)	53s
build (1.85.0, thumbv7em-none-eabi)	13s
test (1.85.0)	17s
test-careful	53s
build (1.85.0, wasm32-unknown-unknown)	18s
build (stable, wasm32-unknown-unknown)	11s
test-miri (x86_64-unknown-linux-gnu)	39s
minimal-versions / minimal-versions	27s
build (stable, thumbv7em-none-eabi)	18s
	4m 24s

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