[clang] [CIR][AArch64] Upstream vector-shift-right-and-insert NEON builtins (PR #196776)

[Andrzej Warzyński via cfe-commits]

banach-space wrote:

Thank you for the updates - this is exactly what I had in mind! And thank you for seeing this through - it's taken us a few iterations, but IMO it's been worth it 🙏🏻 

Could you resolve the conflicts? Once that is sorted, I will land it for you :)

https://github.com/llvm/llvm-project/pull/196776