refactor resolve-scopes pass

[JeffBezanson]

This is a much-needed rewrite of resolve-scopes. Many reasons have accumulated:

• It is one of the slowest lowering passes
• We want to experiment with approaches to solving Global variable scope rules lead to unintuitive behavior at the REPL/notebook #28789
• It will probably need more work in the future as part of a macro hygiene redesign

The code for it has grown quite confusing and unmaintainable, making it hard to address these issues. Hopefully this PR makes it much easier to read and modify. It also removes a bunch of code that was only really needed to deprecate the pre-0.7 global scope behavior, but was hard to tease apart.

So far I have a pretty good first cut that builds and passes test-core and test-syntax. It already fixes some obscure corner cases (see test).

[ViralBShah]

And it is a net deletion of code (at least as of now)!

[JeffBezanson]

Ok, PkgEval identified one problem with underscore handling 🎉 Now this should be ready to go.