Upgrade from Rails 6.1.x to 7.1.x and adjust related dependencies.
- change Rails version in Gemfile
- use Rails 7 compatible versions of dependencies, esp. trln_argon, blacklight-hierarchy, sprockets, sassc-rails
- remove some gems no longer needed, esp. webpacker, coffee-rails
- update version constraints on some gems to get newer major versions
- run bundle update
- run bin/rails app:update and step through each file, resolving changes in bin/ and config/