Separate prelude imports from star imports

[jjcnn]

Description

Fixes #6119 .

Currently, items implicitly imported from the standard library preludes reside in the same namespace as star imports from non-prelude sources. This means that if a star import imports a name that clashes with a name from a prelude, then using that name in the importing module causes an error.

This PR separates the prelude imports into a different namespace, and allows star imports to shadow prelude imports.

Remaining tasks:

• Introduce test that shadowing works.

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 #6971 will not alter performance

_{Comparing jjcnn/prelude_overridden_by_star_import (47f392f) with master (b7d1539)}

Summary

✅ 22 untouched benchmarks