[clang] [CIR][AArch64] Upstream widening-addition NEON builtins (PR #204285)

[Vicky Nguyen via cfe-commits]

iamvickynguyen wrote:

> @iamvickynguyen , looks like @E00N777 beat you to it - "widen" was assigned yesterday before you post this PR 😅 This means that your PR depends on https://github.com/llvm/llvm-project/pull/204088. You can keep your PR as is for now and then just rebase once https://github.com/llvm/llvm-project/pull/204088 lands.

> In the meantime, I have assigned Vector shift left and widen [^](https://arm-software.github.io/acle/neon_intrinsics/advsimd.html#markdown-toc-vector-shift-left-and-widen) to you. Feel free to keep it in this PR.

> @iamvickynguyen I have merged #204088, you could rebase on this commit.

@E00N777 is fast! :rocket: :smile:  Thank you @banach-space and @E00N777 ! :pray:  I'll rebase and continue with this PR and vector shift left and widen.

https://github.com/llvm/llvm-project/pull/204285