Add a Dockerfile for 8.x

SOLR Should have its own Dockerfile, ideally one that is cloud native (i.e. doesn't expect anything special from the operating system in terms of user IDs, etc), for deployment, that we can curate and submit changes to as part of the official ASF process, rather then externally. The idea here is that testing SOLR regression, as a microservice, is something we should be doing as part of our continuous integration, rather then something done externally.

We have a team here that would be more then happy to do the work to port whatever existing SOLR dockerfiles are out there into something that is ASF maintainable, and cloud native, and easily testable, as well.