Allow converting ux types into u128 (and u65 through u127)

It is currently only possible to convert ux types to a maximum type of u64. There are no From impls into u65 through u128. Users of ux types  need to manually do the conversion or call `u128::from(u64::from(n))` .

Documentation showing that the maximum type that u2 can be converted into is u64: https://docs.rs/ux/latest/ux/struct.u2.html#impl-From%3Cu2%3E-for-u64