Unify namespace import logic for parsed and typed declarations

[tritao]

Description

This PR unifies the logic for namespace imports so it works for parsed and typed declarations.

Additionally it collects and handles imports from handling the use statement when collecting.

This allows the soon-to-be-introduced AST resolving pass and collection context to correctly resolve imports.

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.