md4

k12: new implementation with parallel processing support #1512

Job	Run time
minimal-versions / minimal-versions	31s
set-msrv / set-msrv	6s
test (stable)	26s
test (1.85.0)	24s
build (stable, thumbv7em-none-eabi)	19s
build (1.85.0, wasm32-unknown-unknown)	21s
build (1.85.0, thumbv7em-none-eabi)	2m 23s
build (stable, wasm32-unknown-unknown)	2m 23s
	6m 53s

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