Refactor internally generated bounded quantified formulas (#7291)

Refactor internally generated bounded quantified formulas (#7291)

This changes the attribute on internally generated bounded quantified formulas from `isInternal` to `isQuantBounded`. This makes it clear that bounded integers is the module that should process them.  It also moves the utility for constructing these quantified formulas from strings to BoundedIntegers itself.  This is to accommodate other theories, e.g. bags, that may make use of reductions to bounded quantifiers.