[clang] [Clang][AArch64] Lower NEON fcvtz{u/s} intrinsics into fpto{u/s}i.sat (PR #191365)

[David Green via cfe-commits]

davemgreen wrote:

I hadn't realized there was not a constrained.fptosi.sat. It sounds like it would be worth adding one, to allow floats to be converted without the UB. For the moment could we just emit the old intrinsic under Builder.getIsFPConstrained()? My understanding is that you have not removed it.

https://github.com/llvm/llvm-project/pull/191365