[x86] Regenerate a bunch more avx512 test cases using my script to have
tighter, more strict FileCheck assertions. Some of these I really like
as they show case exactly what instruction sequences come out of these
microscopic functionality tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218936 91177308-0d34-0410-b5e6-96231b3b80d8