Remove unnecessary Builder classes

[srawlins]

Big ball of yarn that grew and grew.

The main idea is to remove a bunch of classes, whose necessity I never understood: ElementTypeBuilder (and Impl), ModelElementBuilder (and Impl), ModelObjectBuilder, ModelBuilder, and ModelBuilderInterface. These might have had more of a purpose when we could output to HTML or Markdown, but their complexity is now unwarranted.

The purpose they served is this: In order to fetch a ModelElement or ElementType from from the package graph, you always needed an instance of... the package graph. Putting a *Builder* in a class you're working in gave you a way to instantiate (or fetch from the package graph) a ModelElement or ElementType.

But, lo and behold, we can declare that a Nameable must have a PackageGraph, and then write little utility functions to fetch these things. Much simpler. Here are the other changes needed to facilitate this:

• I renamed the various factory constructors. I generally changed the word 'from' to 'for', because often the value that the factory constructor returns is a cached instance. It feels weird to me to say ModelElement.from some Element, when you know that you already have the instance, and you're just fetching it, using the Element as a key. In that case, I think 'for' is more appropriate.

  • ModelElement._from --> ModelElement.for_
  • ModelElement._fromElement --> ModelElement.forElement
  • ModelElement._fromPropertyInducingElement --> ModelElement.forPropertyInducingElement
  • ElementType._from --> ElementType.for_
  • These did have to be made public, which is unfortunate; I think there are some gymnastics we can do to re-privatize them, but it would more-or-less mean moving Nameable, or a Nameable supertype... I think not worth it.

• Make Nameable a proper mixin. 👍

• Move _resolveMultiplyInheritedElement to be an extension method, to the bottom of the library.

I believe this may also open up nicer refactorings where some late final ElementType fields do not need to be late. It might not be a hole in one, but once we're only relying on packageGraph, we may be able to assign some more instance fields at construction-time.

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[kallentu]

Thank you for doing this. I saw the original ModelBuilder mixins and impls and I wanted to fix it up, so I'm glad you did.