chore: split path and import lookups

[asterite]

Description

Problem

Path and import lookup behave a bit differently. For example you shouldn't have aliases in the middle of a use segment (Rust says they are not modules), and generics can't show up in use statements. This made the code more complex than it should.

Summary

This PR refactors the path lookup code and splits it into two, one to resolve imports and another to resolve paths in places other than imports.

This PR is mainly a refactor that doesn't change how things behave, except that now aliases are forbidden in the middle of a use segment (like in Rust).

The logic to resolve a Path is mostly shared in a resolve_path_kind function, which determines the plain Path and ModuleId where the path should be resolved in. Then traversing that plain path logic is kind of duplicated, once for imports and once for paths in code, but it kind of makes sense because their logic is a bit different and it will continue to diverge as we'll want to solve types with their generics in order to continue finding methods.

Additional Context

Documentation

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.