Removing todo const generics

[xunilrj]

Description

Continuation of #6860.

The summary of removed todo!() are:
1 - Some todo!() are actually unreachable. In future PRs I will try to model the AST better and remove these match arms;
2 - Some are trivial impls like spans;
3 - Some are trivial from traits like PartialEq and PartialOrd.

Others will be removed in future PRs.

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 #7391 will not alter performance

_{Comparing xunilrj/removing-todo-const-generics (27cbf5a) with master (4f1af43)}

Summary

✅ 25 untouched