Simplify handling of subtypes in smt2 printer (#5401)

Simplify handling of subtypes in smt2 printer (#5401)

This makes major simplifications to how subtypes are enforced in the smt2 printer.

It is now the principle that the smt2 prints things faithfully to the AST, regardless of whether it conforms to the smt2 standard.

It also fixes the current smt2 printing of to_real.

Conversely, this removes a hack from GetValueCommand which forced casting via x -> (/ x 1). This is now properly handled in Solver::getValue.

Some regressions change expected output as a result. Notice that internally generated Node may not conform to the smt2 standard, but user-level terms will.