refactor: modular plugins

[dominikg]

this grew rather large but sharing for better discussion

goals:

• split into multiple plugins with clear responsibilities
• separate plugins for preprocess and compile
• fully embrace/adopt environment api
• improve filter use to ensure less work is done in rolldown-vite
• move plugins out of "pre" phase where possible

note: tests currently fail because raw&direct&custom query support hasn't been adapted to the preprocess/compile split

todo: delete dead code in utilities and move functions into plugins where feasible