[llvm] [X86][GlobalISel] Support G_FADD, G_FSUB, G_FMUL, G_FDIV (PR #87339)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

Instead of the lower limit on the clamp (and then scalarizing) - don't we have the option of widening?

https://github.com/llvm/llvm-project/pull/87339