[llvm] [FPEnv] Add strictfp attribute to the FP environment manipulation intrinsics (PR #96093)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> > I think we need an attribute similar to the memory attribute which covers which aspects of the floating-point environment are read/written.
> 
> I'm not sure I see how this is useful. If a strictfp function can safely be called from a non-strictfp function then the caller doesn't need to know these details. 

It's more useful for getting rid of constrained intrinsics, and understanding the behavior of target intrinsics. If we had it, we could tell if strictfp 

For now I think we just need to rely on the callsite attributes and not put these on the declarations 

https://github.com/llvm/llvm-project/pull/96093