k256+primeorder: add `batch_normalize_generic` #149

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	12s
build (1.65.0, wasm32-unknown-unknown)	13s
cross (armv7-unknown-linux-gnueabihf, 1.65.0)	18s
build (stable, thumbv7em-none-eabi)	11s
cross (armv7-unknown-linux-gnueabihf, stable)	24s
build (stable, wasm32-unknown-unknown)	8s
cross (aarch64-unknown-linux-gnu, 1.65.0)	16s
cross (aarch64-unknown-linux-gnu, stable)	38s
doc	7s
cross (powerpc-unknown-linux-gnu, 1.65.0)	13s
test (i686-unknown-linux-gnu, 1.65.0, sudo apt update && sudo apt install gcc-multilib)	45s
cross (powerpc-unknown-linux-gnu, stable)	9s
test (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	31s
test (x86_64-unknown-linux-gnu, 1.65.0)	14s
test (x86_64-unknown-linux-gnu, stable)	35s
	4m 54s

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