Simple utility for transfersing functions such that parent scopes are always
visited before noescape closures.
Note that recursion is disallowed. Noescape closures are not reentrant.
Record noescape closure scopes. This allows passes to process closures and their
parent scopes in a controlled order. AccessEnforcementSelection needs this
because it needs to process parent scopes before selecting enforcement within
noescape closures.
Eventually this could be used by the PassManager so that
AccessEnforcementSelection can go back to being a function transform.
