inout: add `From` impl for splitting `[T; N * M]` into `[[T; N]; M]` … #798

Job	Run time
build (1.85.0, armv7a-none-eabi)	18s
cross (aarch64-unknown-linux-gnu, 1.85.0)	39s
cross (powerpc-unknown-linux-gnu, 1.85.0)	40s
test (x86_64-unknown-linux-gnu, ubuntu-latest, 1.85.0)	17s
cross (powerpc-unknown-linux-gnu, stable)	45s
build (stable, armv7a-none-eabi)	11s
build (stable, wasm32-unknown-unknown)	10s
x86 (x86_64-unknown-linux-gnu, 1.85.0)	22s
test (i686-unknown-linux-gnu, ubuntu-latest, stable, sudo apt update && sudo apt install gcc-mult...	36s
cross (aarch64-unknown-linux-gnu, stable)	43s
test (i686-unknown-linux-gnu, ubuntu-latest, 1.85.0, sudo apt update && sudo apt install gcc-mult...	47s
build (stable, thumbv7em-none-eabi)	18s
x86 (x86_64-unknown-linux-gnu, stable)	23s
minimal-versions / minimal-versions	46s
build (1.85.0, thumbv7em-none-eabi)	13s
test (x86_64-unknown-linux-gnu, ubuntu-latest, stable)	8s
test (x86_64-apple-darwin, macos-latest, stable)	15s
test (x86_64-pc-windows-msvc, windows-latest, stable)	1m 37s
test (x86_64-apple-darwin, macos-latest, 1.85.0)	24s
test (x86_64-pc-windows-msvc, windows-latest, 1.85.0)	29s
build (1.85.0, wasm32-unknown-unknown)	18s
	10m 19s

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