k12: new implementation with parallel processing support (#839) #576

Job	Run time
set-msrv / set-msrv	5s
macos (1.85.0)	32s
macos (stable)	25s
windows (x86_64-pc-windows-gnu, 1.85.0)	1m 5s
linux (x86_64-unknown-linux-gnu, stable)	31s
linux (x86_64-unknown-linux-gnu, 1.85.0)	33s
cross (stable, powerpc-unknown-linux-gnu, default)	45s
windows (x86_64-pc-windows-gnu, stable)	1m 15s
cross (1.85.0, aarch64-unknown-linux-gnu, default)	45s
cross (stable, aarch64-unknown-linux-gnu, default)	40s
build (1.85.0, wasm32-unknown-unknown)	25s
cross (1.85.0, powerpc-unknown-linux-gnu, default)	40s
build (stable, loongarch64-unknown-linux-gnu)	28s
build (stable, thumbv7em-none-eabi)	21s
build (stable, wasm32-unknown-unknown)	25s
build (1.85.0, loongarch64-unknown-linux-gnu)	21s
build (1.85.0, thumbv7em-none-eabi)	25s
	9m 41s

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