Publish test jar as part of the release

[ben-manes]

Sometimes projects may need to embed part of JCTool's and can benefit by reusing some of the test infrastructure. This is a use at your own risk type of option, but is very low effort to offer with that expected caveat. By following the Maven's Guide to using attached tests, an additional artifact is available with the tests classifier. For example, this way Caffeine could reuse your QueueSanityTest rather than copying it in locally.