Fix issue with __transmute type checking

[xunilrj]

Description

This PR solves an issue with __transmute in "const contexts". In these cases, the "source" and "return" types were not being correctly solved.

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 #6940 will not alter performance

_{Comparing xunilrj/fix-transmute-type-checking (c8a845c) with master (6de04fc)}

Summary

✅ 22 untouched benchmarks