ci: Add Rails 7.2 and Ruby 3.3 to testing matrix

[hasghari]

No description provided.

[hasghari]

This fixes the following deprecation warning:

warning: query string used for GET parsing different from current query string. Starting in Rack 3.2, Rack will used the cached GET value instead of parsing the current query string.

[sej3506]

There are a number of files deleted in this PR. Could you add a description and some information about what this PR is doing beyond updating the test matrix?

[hasghari]

There are a number of files deleted in this PR. Could you add a description and some information about what this PR is doing beyond updating the test matrix?

@sej3506 Sure. I've tried to have descriptive commit messages for each of the 6 commits in this PR. However, the commit with the subject "Use default settings of Rails version under test" is the most substantial one. Many of the deprecation warnings that were produced were a result of testing different versions of Rails with non-default settings. My goal with that specific commit was to set config.load_defaults Rails::VERSION::STRING.to_f so that the default settings would be applied for testing the specific version of Rails under test.

I also wanted to standardize the setup of a dummy application for testing purposes so I generated the dummy application structure by copying the files generated by running rails plugin new. This ends up simplifying the configuration and removing some of the monkey-patching that was necessary in the old setup.