rc4: add basic benches (#544) #901

Job	Run time
build (1.85.0, thumbv7em-none-eabi)	20s
build (1.85.0, wasm32-unknown-unknown)	22s
minimal-versions / minimal-versions	19s
build (stable, thumbv7em-none-eabi)	13s
test (1.85.0)	20s
build (stable, wasm32-unknown-unknown)	26s
test (stable)	18s
	2m 18s

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