Solr upgrade extraction

[candyhazlett]

includes:

• solr version update to 8
• updates ruby version
• removes hydra/fedora gems and references in codebase
• adds dependabot security updates

[amclark42]

It looks like SolrService.query was specific to ActiveFedora. Some instances of it already marked with "TODO" comments, so they'll be easy to find and replace later. I've added a To Do item to the Solr upgrade card in Trello to figure out replacement code using Blacklight or Rsolr.

Edit: Just in case, the files with outdated references are:

• app/models/concerns/solr_helpers.rb
• app/models/concerns/tapas_queries.rb
• app/models/solr_document.rb
• app/validators/core_file_validator.rb
• app/views/catalog/_index_default.html.haml