Switch constantIsGreaterEqual to use greaterEqual

[Scottbruceheart]

There isn't an advantage to using the previous algorithm.

[thecppzoo]

Please prove the claim there's no advantage to using the older mechanism, for all cases.

[Scottbruceheart]

I think there is an advantage for the msb_off version, though?

[Scottbruceheart]

I believe we also previously posted godbolt results for both that showed the general version of the constant compare (constantIsGreaterEqual) is more operations than the taocp impl.