dynamic infobox on javadocs/tutorials/ref-guide html pages when URL doesn't match "latest" version [LUCENE-7924]

Spinning this idea out of some comments/concerns in [SOLR-10595](https://issues.apache.org/jira/browse/SOLR-10595)...

It would be nice if all the various "version specific" pages we have (ie: javadocs, tutorials, solr ref-guide) could include some standard snippet of text drawing users attention to the fact that they are looking at docs for an "older" version of lucene/solr – ideally with a link to the current version. ala...

> This page is part of the documentation refers to Lucene 5.4.0. The current version of [Lucene is 6.6.0](http://lucene.apache.org/core/6_6_0/core/).

The details of how this could work aren't clear cut – particularly since for any arbitrary URL the "latest" version of those docs may not contain the exact same path/file (ie: deprecated/moved classes in future releases, etc...) but ideally it would be some very generic mod_include / javascript directive that could be included in all generated HTML, that would only "activate" when the page was loaded from lucene.apache.org and would only inject the "warning" into the page based on the version number in the URL compared to some server side configured version number (ex: the way we already have the "latest" version# hardcoded in our .htaccess file for redirects)

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Migrated from [LUCENE-7924](https://issues.apache.org/jira/browse/LUCENE-7924) by Chris M. Hostetter (@hossman)
Linked issues:
- [SOLR-10595](https://issues.apache.org/jira/browse/SOLR-10595)