Enable storage_vec_iter_tests in-language test

[ironcev]

Description

This PR brings the storage_vec_iter_tests in-language test to the newest compiler version and enables it. The test was originally disabled because of #6899 which has been fixed.

To bring the test to the newest compiler version, this PR:

• fixes trait coherence violations.
• adds support for const_generics experimental feature.

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 #7356 will not alter performance

_{Comparing ironcev/enable-storage-vec-iter-tests (fc8cad4) with master (8fa01b8)}

Summary

✅ 25 untouched benchmarks