Add SVE2 instructions to SIMD.

[aserputov]

Hello, Vc
I would like to try and implement the SVE2 instruction into the code. I appreciate any comments and advice on this. Thank you.
https://developer.arm.com/documentation/102340/0001/Introducing-SVE2

[amadio]

You are welcome to work on Vc if you want. However, you should know that Vc is no longer being actively developed. You may want to consider focusing your work in the std::experimental::simd implementation instead (available with GCC 11 and above).

[aserputov]

@amadio did you finish working on NEON in Vc? Or how is progress going in std::experimental::simd ? Could guide me please ?

[amadio]

I think @mattkretz would know better the answer to the questions above. I believe that the work in the C++ standard already has support for NEON on ARM/ARM64, I don't know if support for it was completed in Vc, I've only used Vc_IMPL=Scalar on ARM myself.