Use HashSet for error deduplication

[ylmin]

Description

Optimization Explanation

• Using HashSet to track seen elements simplifies the code logic.
• Using the retain method directly filters out duplicate elements in place, avoiding the complexity of manually managing indices and swapping elements.
• The code is more concise and readable while maintaining the original order.
• Time complexity comparison: Original code: Due to the need to manually manage indices and swap elements, the time -complexity is O(n^2) (in the worst case). Optimized code: Using HashSet and the retain method, the time complexity is O(n).
• Space complexity comparison: Original code: Requires additional HashMap and SmallVec to store hash values and indices. Optimized code: Only requires a HashSet to store seen elements.

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.

[IGI-111]

Clever.