Implement ge and le for U128

[mohammadfawaz]

#3053 attempts to introduce ge and le. Sadly, to do this properly, we need to be able to write

impl core::ops::OrdEq for U128 {
    fn ge(self, other: Self) -> bool {
        ...
    }

    fn le(self, other: Self) -> bool {
        ...
    }
}

which doesn't work (yet) due to #1667

[bitzoic]

Closed by #6048