[VFS-500] implement VFSClassLoader.findResources and test

This adds VFSClassLoader.findResources() as well as a Unit test. The test is rather complicated to work with all the providers (actually skip most of them). An option would be a TestCase which is not added to all provider tests.

The unit test also verifies actual resource loading from JAR searchPath.

(btw: this is also a test for INFRA-6764 if the pull request mails are received by dev@)