[clang] [CIR][Aarch64] upstream scalar & vector intrinsics (FP16) (PR #190310)

[Andrzej Warzyński via cfe-commits]

https://github.com/banach-space approved this pull request.

LG % nit, thank you for contributing!

Btw, would you be able to and interested in the remaining builtins from https://arm-software.github.io/acle/neon_intrinsics/advsimd.html#vector-arithmetic-3 ?

https://github.com/llvm/llvm-project/pull/190310