[llvm] [CodeGen] Provide `MachineFunction::hasUnsafeFPMath` (PR #127488)

[via llvm-commits]

paperchalice wrote:

> What's the story for folks that're using `Options.UnsafeFPMath`? Do they need to migrate to using the attribute instead?

Some backends use this option to control the behavior of legalizer. Ideally backend should consider both `Options.UnsafeFPMath` and "unsafe-fp-math" function attribute.

https://github.com/llvm/llvm-project/pull/127488