k12: new implementation with parallel processing support #555

Job	Run time
set-msrv / set-msrv	4s
cross (1.85.0, aarch64-unknown-linux-gnu, default)	37s
macos (1.85.0)	32s
windows (x86_64-pc-windows-gnu, stable)	1m 38s
macos (stable)	31s
windows (x86_64-pc-windows-gnu, 1.85.0)	1m 24s
cross (stable, powerpc-unknown-linux-gnu, default)	39s
linux (x86_64-unknown-linux-gnu, 1.85.0)	15s
cross (stable, aarch64-unknown-linux-gnu, default)	46s
build (1.85.0, thumbv7em-none-eabi)	21s
cross (1.85.0, powerpc-unknown-linux-gnu, default)	2m 25s
build (stable, wasm32-unknown-unknown)	31s
linux (x86_64-unknown-linux-gnu, stable)	2m 25s
build (1.85.0, loongarch64-unknown-linux-gnu)	27s
build (stable, thumbv7em-none-eabi)	2m 25s
build (stable, loongarch64-unknown-linux-gnu)	2m 25s
build (1.85.0, wasm32-unknown-unknown)	2m 25s
	19m 50s

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