sec1: replace `subtle` with `ctutils` #3401

Job	Run time
test (1.85.0)	52s
test (stable)	45s
build (stable, wasm32-unknown-unknown)	20s
build (1.85.0, thumbv7em-none-eabi)	23s
minimal-versions / minimal-versions	54s
build (1.85.0, wasm32-unknown-unknown)	26s
build (stable, thumbv7em-none-eabi)	23s
	4m 3s

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