translate previous scalarset values through schedule when printing

Prior to this commit, we were diffing scalarset values during printing against
their raw representation, rather than their permuted value. Depending on your
perspective, this is either wrong or inaccurate. It would result in scalarset
fields in a diff counterexample trace (the default) sometimes being incorrectly
suppressed and sometimes being incorrectly shown.

Note that there is more work to be done here, as this does not address the
equivalent for scalarset indexed arrays.

Github: related to #194 "clearer CEX output with scalarsets"