RFR [9] 8152277: Move URLClassPath.pathToURLs(String) to RegistryImpl

[Chris Hegarty]

In the context of 8149122 & 8152190 it was noticed that
sun.rmi.registry.RegistryImpl is the only invoker of URLClassPath::pathToURLs.
Rather that adding a qualified export to java.rmi for this, it makes sense to move
pathToURLs(String) to RegistryImpI ( and "modernize" the implementation a little ).

http://cr.openjdk.java.net/~chegar/8152277/
https://bugs.openjdk.java.net/browse/JDK-8152277

-Chris.