Add Ruby 3.1 and Rails 7 to CI

[petergoldstein]

This PR adds the Ruby 3.1 and Rails 7 elements to the CI matrix. To support those changes a number of other changes were required:

• Adding a basic Rails 7 Gemfile and updating Appraisals
• Quoting 3.0 in the .github/workflows/build.yml file so that this entry pulls Ruby 3.0.x and not Ruby 3.1
• Adding the "--disable-error_highlight" value for RUBYOPT in the build environment to disable Ruby 3.1 error highlighting
• Bumping the version of standard to pick up a Ruby 3.1 compatible Rubocop version
• Disabling the standard run for bundle exec rake for Rails version >= 3.1.0 because of a conflicting evaluation for Style/MethodMissingSuper for Ruby 3.1 and earlier Rubies

[composerinteralia]

Thanks! It may be slightly easier to add Rails and Ruby separately, since there are quite a few changes here.

[petergoldstein]

@composerinteralia Ok, this is all green now. Let me know if you still want to split it into two different PRs.