Refactor type resolve to deal with ResolvedDeclaration.

[tritao]

Description

Refactor type resolving to deal with ResolvedDeclaration instead of just ty::TyDecl.

Allows further re-use of this code to deal with parsed declarations too.

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 #6659 will degrade performances by 16.87%

_{Comparing tritao:type-resolve-resolved (ab48ec9) with master (029c593)}

Summary

❌ 1 regressions
✅ 21 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	master	tritao:type-resolve-resolved	Change
❌	document_symbol	4.4 ms	5.3 ms	-16.87%

[tritao]

Closing in favour of #6660.