WIP: Add annotation to register scope contexts

[sixcorners]

Think it would be nice if I could register a context at build time without creating an extension?

[sixcorners]

Also what about making InjectableContext.destroy() call InjectableContext.destroy(ContextState)?

[sixcorners]

nevermind. I see now that I can just define a ComponentsProvider to register these things. Neato!

import org.kohsuke.MetaInfServices;

@MetaInfServices
public class MyComponentsProvider implements ComponentsProvider {
  @Override
  public Components getComponents() {
    return new Components(
        List.of(),
        List.of(),
        List.of(new MyContext()),
        Set.of(),
        Map.of(),
        List::of,
        Map.of(),
        Set.of(),
        Map.of());
  }
}