Check for type aliases when implementing traits

[jjcnn]

Description

Fixes #6329 .

During insertion of impls into the trait map we used to forget to check for alias types, which meant that it was possible to have multiple implementations of a trait for the same type, one for the original type and one for the alias.

#6626 fixed this bug, but the error message was unhelpful in that it reported the error on the original type without mentioning the alias.

This PR improves the error message, and also improves the error message for aliased types when they contain multiple declarations of the same member.

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
  • If my change requires substantial documentation changes, I have requested support from the DevRel team
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.

[codspeed-hq]

CodSpeed Performance Report

Merging #6875 will not alter performance

_{Comparing jjcnn/unalias_type_id_in_trait_map_unification (05322d7) with master (8c0cc20)}

Summary

✅ 22 untouched benchmarks

[tritao]

Sorry to be the bad cop, just a few minor whitespace issues