[llvm] [Intrinsics][AArch64] Add intrinsic to mask off aliasing vector lanes (PR #117007)

[Sander de Smalen via llvm-commits]

https://github.com/sdesmalen-arm commented:

Apologies for the delay, this review was much overdue. I've left some comments to tidy up some of the changes and also a bunch of nits. But overall it looks good!

https://github.com/llvm/llvm-project/pull/117007