Previously when converting from HIR -> ReactiveFunction we elided break/continue
terminals in places where control would implicitly transfer to the
break/continue target and therefore nothing has to be emitted. The one downside
of this approach is that it makes scope analysis a bit trickier. We want to
close scopes once we see an instruction id past the end of the scope's range,
but these implicit breaks were causing us to miss some instruction ids. We
compensated for this, but it's helpful to keep the representation explicit and
discard these terminals later in codegen.