[llvm] Reapply "[msan] Add avx512-intrinsics.ll and avx512-intrinsics-upgrade.ll test case (#123980)" (PR #124500)

[Thurston Dang via llvm-commits]

thurstond wrote:

> > I had reverted the original patch because of buildbot failures (e.g., https://lab.llvm.org/buildbot/#/builders/13/builds/4938/steps/5/logs/FAIL__LLVM__avx512-intrinsics-upgrade_ll). This reland addresses the likely root cause; namely, that the target datalayout had not been specified.
> 
> It can be more convenient to review reland, it consist of 2 commits, "revert of revert", and fixes however, if fix is trivial, no need to request a new review

I've split the commit into "revert of revert" + the fix.

> Is possible to fix "undef deprecator" ?

Since these are MSan tests, and we want to know how MSan deals with uninitialized memory, undef seems appropriate?

https://github.com/llvm/llvm-project/pull/124500