Core reflection's generic signature parsing uses an ancient library with outdated visitor pattern on a tree model and contains unnecessary boilerplates. This is a duplication of ClassFile API's signature model. We should just move to ClassFile API, which is more throughoutly tested as well.

This migration will not affect the implementation classes of java.lang.reflect.Type, except the lazy expansion will happen from the CF tree objects instead of legacy tree objects. New regression tests will ensure backward-compatible behavior with malformed signatures and missing classes or interfaces in signatures.