k256

sm2: add SM2PKE support #2215

Job	Run time
benches (1.73.0)	1m 23s
build (1.73.0, thumbv7em-none-eabi)	45s
benches (stable)	1m 20s
build (1.73.0, wasm32-unknown-unknown)	44s
cross (armv7-unknown-linux-gnueabihf, 1.73.0)	1m 29s
cross (armv7-unknown-linux-gnueabihf, stable)	1m 19s
doc	57s
cross (aarch64-unknown-linux-gnu, 1.73.0)	1m 25s
test (i686-unknown-linux-gnu, 1.73.0, sudo apt update && sudo apt install gcc-multilib)	1m 41s
build (stable, thumbv7em-none-eabi)	46s
cross (aarch64-unknown-linux-gnu, stable)	1m 34s
test (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	1m 37s
build (stable, wasm32-unknown-unknown)	42s
cross (powerpc-unknown-linux-gnu, 1.73.0)	1m 24s
test (x86_64-unknown-linux-gnu, 1.73.0)	1m 32s
cross (powerpc-unknown-linux-gnu, stable)	1m 12s
test (x86_64-unknown-linux-gnu, stable)	1m 26s
	21m 16s

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