[msan] Add avx512-intrinsics-upgrade.ll test case

This is forked from llvm/test/CodeGen/X86/avx512-intrinsics-upgrade.ll.
It tests intrinsics that LLVM "auto-upgrades"; for example,
@llvm.x86.avx512.mask.store is converted into @llvm.masked.store (which has the interesting side effect that MemorySanitizer can already handle it via its existing handleMaskedStore).

Author: thurstond