k256+primeorder: add `BatchInvert` and `BatchNormalize` impls #133

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	6m 11s
build (1.65.0, wasm32-unknown-unknown)	5m 33s
build (stable, thumbv7em-none-eabi)	59s
build (stable, wasm32-unknown-unknown)	24s
cross (armv7-unknown-linux-gnueabihf, 1.65.0)	7m 2s
doc	15s
cross (armv7-unknown-linux-gnueabihf, stable)	1m 8s
cross (aarch64-unknown-linux-gnu, 1.65.0)	4m 43s
test (i686-unknown-linux-gnu, 1.65.0, sudo apt update && sudo apt install gcc-multilib)	4m 48s
cross (aarch64-unknown-linux-gnu, stable)	2m 38s
test (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	2m 34s
cross (powerpc-unknown-linux-gnu, 1.65.0)	8m 21s
test (x86_64-unknown-linux-gnu, 1.65.0)	4m 28s
cross (powerpc-unknown-linux-gnu, stable)	2m 3s
test (x86_64-unknown-linux-gnu, stable)	50s
	51m 57s

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