CI: update build matrix - Ruby 3.3 & Rails 7.1

[orien]

• Add Ruby 3.3 and Rails 7.1
• Move EOL Rails versions to the lower section, with one build each.
• Introduce a dedicated section for Ruby 2.7 and Ruby 3.0. The next version of Rails won't work with these.
• Specify the Ubuntu version for each build job. Older versions of Ruby segfault on newer versions of Ubuntu.

[orien]

@albus522 All CI jobs passing, except the jruby-head ones!

[albus522]

I noticed this after I had dug myself out of the weeds. This would have been a better starting point. I did pull your ubuntu release pinning over.