[mlir][arith] Introduce `minnumf` and `maxnumf` operations (#66429)

This patch is part of a larger initiative aimed at fixing floating-point
`max` and `min` operations in MLIR:
https://discourse.llvm.org/t/rfc-fix-floating-point-max-and-min-operations-in-mlir/72671.

Here we introduce new operations for floating-point numbers: `minnum`
and `maxnum`.
These operations have different semantics than `minumumf` and `maximumf`
ops.
They follow the eponymous LLVM intrinsics semantics, which differs
in the handling positive and negative zeros and NaNs.

This patch addresses the 1.3 task from the RFC.