Pluginfy RuboCop RSpec

[koic]

This PR adds support for RuboCop's Plugin feature: rubocop/rubocop#13792

It replaces the ad-hoc Inject with RuboCop plugins introduced in RuboCop 1.72.

NOTE: Version 1.72.1 or later is specified, as it includes rubocop/rubocop#13837, which removes the Inject from spec_helper.rb. While 1.72.0 is sufficient for runtime, but specifying the patch version 1.72.1 keeps things simple.

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Before submitting the PR make sure the following are checked:

• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Updated documentation.
• Added an entry to the CHANGELOG.md if the new code introduces user-observable changes.
• The build (bundle exec rake) passes (be sure to run this locally, since it may produce updated documentation that you will need to commit).

If you have created a new cop:

• Added the new cop to config/default.yml.
• The cop is configured as Enabled: pending in config/default.yml.
• The cop is configured as Enabled: true in .rubocop.yml.
• The cop documents examples of good and bad code.
• The tests assert both that bad code is reported and that good code is not reported.
• Set VersionAdded: "<<next>>" in default/config.yml.

If you have modified an existing cop's configuration options:

• Set VersionChanged: "<<next>>" in config/default.yml.

[bquorning]

Our users will not be able to continue using require in their config file, right? They need to start using plugins instead?

[bquorning]

CI is failing because module RuboCop::RSpec::Plugin#about never gets called. Would it make sense to make an assertion on e.g.

env = Struct.new(:config_store).new(RuboCop::ConfigStore.new))
RuboCop::Version.extension_versions(env)

including the string "rubocop-rspec"?

[koic]

Our users will not be able to continue using require in their config file, right? They need to start using plugins instead?

For compatibility, the old require specification will still work. However, warning will be displayed to encourage updating to plugins. Therefore, users can replace it with plugins at any time.

[koic]

CI is failing because module RuboCop::RSpec::Plugin#about never gets called.

Sorry, Plugin#about is something that gets called back from the RuboCop engine, so to be honest, I’m not sure if this coverage is meaningful.

[koic]

Note, a simple plugin migration guide is available for reference:
https://docs.rubocop.org/rubocop/1.72/plugin_migration_guide.html

[bquorning]

cc @pirj, @ydah

[pirj]

Nice!

I’m away from my computer for a few days and can’t test manually.

[bquorning]

Thank you @koic 🙏🏼

[ydah]

Thank you!