[llvm] Add SPIRV lowering for intrinsics @llvm.fptosi.sat.* and @llvm.fptoui.sat.* (PR #125805)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

I'm a little concerned that this isn't using existing GlobalISel legalization infrastructure; LegalizerHelper::widenScalar already has code to handle widening G_FPTOSI_SAT.

https://github.com/llvm/llvm-project/pull/125805