Drop EOL ruby versions

[mjankowski]

From the studio that brought you standardrb/standard#633 and standardrb/standard-rails#42 comes ... this PR.

• Bump actions/checkout on CI (removes deprecation warning)
• Drop EOL rubyies (2.7 and 3.0) from CI config
• Add latest stable (3.3) ruby to CI config
• Drop various ruby-2.7-specific conditional checks around gem/test/etc

I did NOT yet bump the required ruby version in the gemspec ... can do so here or in subsequent PR if desired.

[searls]

My 2¢: if everything works fine under Ruby 3.0, I'd rather keep it in the matrix (this goes for standardrb/standard, too, I just realized your previous PR also dropped 3.0 there), so that (1) we know whether it works and (2) we raise required_ruby_version to 3.0 instead of jumping straight from 2.7 to 3.1.

As for releasing the gems with a higher required_ruby_version, I think all of the core gems (standard, -performance, -custom) should move this property in lock step with one another, regardless. (I realize they're already out of sync). @camilopayan, thoughts on coordinating?

[mjankowski]

Fair enough, makes sense to keep CI covering all supported versions, and I also see the argument for "lets only bump one marjor version at a time" in the gemspec.

Just pushed commit here to restore 3.0 to CI matrix, and bump to 3.0.0 in the gemspec.

Opened standardrb/standard#634 and standardrb/standard-rails#44 to coordinate if desired.

[searls]

Thanks for plugging away at all this @mjankowski -- there is one more included-by-default gem: https://github.com/standardrb/standard-custom you might want to look at for consistency

[mjankowski]

Cool - will hit that one next.

One random aside here ... https://github.com/standardrb/standard/blob/v1.37.0/config/default.yml#L3 should TargetRubyVersion in standard/default.yml be kept aligned with whatever the lowest supported ruby version in standard is? I'm thinking probably?

[searls]

One random aside here ... https://github.com/standardrb/standard/blob/v1.37.0/config/default.yml#L3 should TargetRubyVersion in standard/default.yml be kept aligned with whatever the lowest supported ruby version in standard is? I'm thinking probably?

… yes?

As is probably clear to you now this process is involved enough that the main repo would probably benefit from a brief documentation file explaining how to bump base Ruby version across all built-ins and plugins.

Sorry this is so sprawling!