std_detect: add avx512fp16 #1886

Job	Run time
Check Style	12s
Test (i686-unknown-linux-gnu)	57s
Build Documentation	1m 5s
Test (x86_64-unknown-linux-gnu)	53s
Env Override	12s
Build std_detect	1m 2s
Test (x86_64-unknown-linux-gnu-emulated)	53s
Automatic intrinsic verification	28s
Test (arm-unknown-linux-gnueabihf)	53s
Test (armv7-unknown-linux-gnueabihf)	55s
Test (aarch64-unknown-linux-gnu)	53s
Test (riscv64gc-unknown-linux-gnu)	45s
Test (powerpc64le-unknown-linux-gnu)	57s
Test (s390x-unknown-linux-gnu)	39s
Test (wasm32-wasi)	55s
Test (i586-unknown-linux-gnu)	55s
Test (nvptx64-nvidia-cuda)	32s
Test (thumbv6m-none-eabi)	11s
Test (thumbv7m-none-eabi)	16s
Test (thumbv7em-none-eabi)	13s
Test (thumbv7em-none-eabihf)	16s
Test (aarch64-apple-darwin)	43s
Test (x86_64-pc-windows-msvc)	50s
Test (i686-pc-windows-msvc)	47s
Test (x86_64-apple-darwin, macos-11)	53s
	17m 15s

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