Plugins need to own first-class options

[som-snytt]

With the dawn of "toolkit composition", where it's easy for scala-cli to create a compiler with required dependencies, including plugins, third party plugins need first-class access to the compiler option namespace.

In particular, plugins that generate warnings deserve to own -W switches.

Today's example is the zero waste plugin, the last blocker for production use of Scala 3.

I'll volunteer to take a first swing at whether it is feasible for competing plugins to declare which options they support.

The second-class -P mechanism, which is great for people who love colons, and who does not love colons, does not inspire confidence.

Maybe -V can profit from the mechanism.

[SethTisue]

I'm lightly skeptical... -P seems fine to me 🤷 , and I'm not sure it's a good idea to blur the distinction in user's minds between what the compiler provides and what a plugin provides

[som-snytt]

The goal is for compiler to do less providing. It may turn out to be untenable.

[som-snytt]

This idea is more interesting if the compiler generates no warnings and all -W output is 3rd-party. Same for lints, which are just a class of warnings.