Split the stdsimd feature into separate features #1846

Job	Run time
Check Style	21s
Env Override	18s
Automatic intrinsic verification	36s
Build Documentation	1m 20s
Build std_detect	1m 24s
Test (i686-unknown-linux-gnu)	3m 34s
Test (x86_64-unknown-linux-gnu)	6m 42s
Test (x86_64-unknown-linux-gnu-emulated)	12m 24s
Test (arm-unknown-linux-gnueabihf)	2m 29s
Test (armv7-unknown-linux-gnueabihf)	13m 1s
Test (aarch64-unknown-linux-gnu)	13m 21s
Test (riscv64gc-unknown-linux-gnu)	2m 32s
Test (powerpc64le-unknown-linux-gnu)	6m 35s
Test (s390x-unknown-linux-gnu)	3m 14s
Test (wasm32-wasi)	3m 4s
Test (i586-unknown-linux-gnu)	3m 20s
Test (nvptx64-nvidia-cuda)	44s
Test (thumbv6m-none-eabi)	18s
Test (thumbv7m-none-eabi)	18s
Test (thumbv7em-none-eabi)	16s
Test (thumbv7em-none-eabihf)	20s
Test (aarch64-apple-darwin)	2m 8s
Test (x86_64-pc-windows-msvc)	9m 45s
Test (i686-pc-windows-msvc)	4m 54s
Test (x86_64-apple-darwin, macos-11)	7m 20s
	1h 40m 18s

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