Ruby: Support Herb in Ractors

[joelhawksley]

Summary

• mark the Ruby native extension as Ractor-safe
• exercise parsing, lexing, extraction, diffing, and version access concurrently
• support both the legacy and Ruby 4 Ractor result APIs in the test

Testing

• bundle exec ruby -Itest test/herb_test.rb on Ruby 3.3.12
• bundle exec ruby -Itest test/herb_test.rb on Ruby 4.0.6
• bundle exec rake test on Ruby 4.0.6
• bundle exec rubocop test/herb_test.rb --format quiet

[marcoroth]

Hey @joelhawksley, I'm not sure if we can just set rb_ext_ractor_safe(true) without changing anything about the code.

Ractor-safety wasn't in the scope of my thinking when I designed the parser and the Ruby C-Extension. So I'm not certain that it's just compatible as-is.

[joelhawksley]

@marcoroth I'll move this back to draft and investigate further. I was poking around at various ways of speeding up our usage of ActionView::Precompiler with Herb ❤️. For what it's worth, I was able to use Herb in Ractors successfully.

[marcoroth]

Thanks @joelhawksley, that's valuable feedback and makes this decision a bit easier down the road!

I know that @geeksilva97 mentioned to me at RubyConf a few weeks ago that he found some issues with Ractors and Herb. Edy, would you mind elaborating what you found? Thank you!