[clang] [CIR][AArch64] Upstream Neon vget_lane/vgetq_lane builtins (PR #186119)

[Andrzej Warzyński via cfe-commits]

https://github.com/banach-space commented:

> Hey I have made several changes accordingly can you review them

Great thank you for the updates! I've left my final comments inline. Thank you for working on this!

Btw, are you planning to implement `vdup` builtins from https://arm-software.github.io/acle/neon_intrinsics/advsimd.html#extract-one-element-from-vector as well? No worries if not - I am asking so that I can plan accordingly :)

https://github.com/llvm/llvm-project/pull/186119