Fix avx512vl_{128,256} correctness bugs + CI default-arch typo#1357

JohanMabille merged 2 commits into

xtensor-stack:masterxtensor-stack/xsimd:masterfrom

DiamonDinoia:fix/avx512vl-known-issuesDiamonDinoia/xsimd:fix/avx512vl-known-issuesCopy head branch name to clipboard