Solr needs its own Version class

From 9.0 on, Solr may release with a different version number than the Lucene it depends on, since Lucene is just another jar dependency now.

Several places in our code base we either print a version based on Lucene Version, or make other decisions based on it. It's still the correct Version to use for index compatibility and analysis plugins, but other places we need a SolrVersion to replace it.