Contract self impl

[xunilrj]

Description

Continuation of #7030.

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 #7275 will not alter performance

_{Comparing xunilrj/contract-self-impl (c4c45e6) with master (403a7e5)}

Summary

✅ 25 untouched benchmarks

[tritao]

By the way, realized we probably want to add some docs regarding this new functionality.

[xunilrj]

By the way, realized we probably want to add some docs regarding this new functionality.

Done.