Ruby 3.3 support

[sengi]

https://www.ruby-lang.org/en/news/2023/12/25/ruby-3-3-0-released/

Looks like we might need to start building yjit 🦀🦀🦀 (fair enough, we've put it off for quite some time and apparently the RAM tradeoff is less awful than it used to be). Nah it's still optional even for projects that pull in the new initializer. 🥾🥫🛣️ #65