add avx512 to panama provider

[akash-shankaran]

Add AVX512 support for Dot Product

[ashkrisk]

AVX512 should automatically be picked up by dotProductPreferred, since the preferred vector species will already be SPECIES_512 on supported platforms. If I'm not mistaken, this PR is primarily useful for future-proofing in cases where a bigger vector species might exist (say 1024-bits), but the vector length is in-between 512 and 1024 bits. As a suggestion, how about changing the PR title to reflect that?

[marianotepper]

@ashkrisk is right. Until wider SIMD instructions become available, we should be good with the "preferred" implementation.

[akash-shankaran]

Makes sense. Thanks for your comments @ashkrisk and @marianotepper. I didn't realize the dotProductPreferred covered the AVX512 case, which is what I was trying to add.

I don't think its worth adding code to future-proof the implementation, and we can wait for wider SIMD registers to be available in hardware. I'll close the PR for now.