[CIR] Add nofpclass for fast-math flags (#191455)
When `-menable-no-infs` or `-menable-no-nans` is set, OGCG adds
`nofpclass(nan inf)` to FP arguments and return values. CIR was missing
this.
Adds the check in `constructFunctionReturnAttributes` and
`constructFunctionArgumentAttributes`, gated on
`hasFloatingRepresentation()` (same condition classic codegen uses in
`canApplyNoFPClass`).
The MLIR LLVM dialect already has `llvm.nofpclass` from #188374, so only
the CIRGen side is needed here.
Test covers float, double, `_Complex double`, and a non-FP control case.
Made with [Cursor](https://cursor.com)
