md5

k12: new implementation with parallel processing support #1333

Job	Run time
set-msrv / set-msrv	5s
minimal-versions / minimal-versions	28s
test (stable)	30s
test (1.85.0)	30s
build (stable, thumbv7em-none-eabi)	25s
build (1.85.0, wasm32-unknown-unknown)	23s
build (1.85.0, thumbv7em-none-eabi)	4m 28s
build (stable, loongarch64-unknown-linux-gnu)	22s
build (1.85.0, loongarch64-unknown-linux-gnu)	23s
build (stable, wasm32-unknown-unknown)	21s
	7m 55s

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