Consider removing Instruction::Truncate in favour of modulo binary instructions

[TomAFrench]

As noted in #4329, Instruction::Truncate is just a special case of the modulo operator. @jfecher raised the potential for just removing the truncation instruction and working in terms of the modulo operator generally.

We should look into whether that would result in simplifications to the compiler logic or whether handling the special cases of power of 2 moduli would be extra verbose with this method.