Always return tupled_upvar_tys for Closure/Generator consituent tys

Always return tupled_upvar_tys for Closure/Generator consituent tys

Depending on if upvar_tys inferred or not, we were returning either an
inference variable which later resolves to a tuple or else the upvar tys
themselves

Co-authored-by: Roxane Fruytier <roxane.fruytier@hotmail.com>