[clang] [CIR][AArch64] Upstream addition and polynomial-addition NEON builtins (PR #202005)

[Andrzej Warzyński via cfe-commits]

banach-space wrote:

> > Great, thank you!
> > Before landing this, could you move the new tests to neon/add.c instead of neon/intrinsics.c? The latter is already too large and we should split it at some point.
> 
> Sure! I've moved the polynomial-addition tests to neon/add.c.

Oh, I actually meant _all_ of the new tests, sorry for not being clearer. Fixed here:
* https://github.com/llvm/llvm-project/pull/203543

Could you approve? Thanks!

https://github.com/llvm/llvm-project/pull/202005