Set up bench dir with JMH project and runner harnesses #9807

We have various benchmarks in the bench dir and scattered other places in the codebase (such as the JMH benchmarks from #9794). This issue is to get the bench dir cleaned up, with harnesses for running from Ruby, fetching or managing other known suites (like those used by the YJIT folks) and a Maven project to run JMH against JRuby without shipping those benchmarks.