The ICUJDKComparison tool doesn't handle overloaded APIs properly. it needs to
detect when we have no overload that handles a JDK method that we're mirroring,
not just that we have come corresponding overload.
Not clear whether this needs to be merged with or share code with the API
comparison tool, some parts are quite similar.
Need to handle cases where JDK method is abstract and ours is not, this should
be ok but the tool needs to recognize that.
This is needed to ensure we truly are a superset of the JDK.