early review sought: https://github.com/pantsbuild/pants/pull/22248 introduces a "library style" backend/plugin initialization API. I'd love some early feedback on the naming of classes and functions and general approach. (The API basically allows a plugin to be called in an imperative manner versus Pants calling various "framework style" methods like

target_types

and

rules

. Will benefit out-of-tree plugins which want a chance to run some logic consistently before registering things with the engine.)