Artemis: Refactor and Optimize Methods in Double Class for Performance Improvements

[mike-turintech]

This pull request refactors and optimizes several methods in the Double class, specifically targeting sumSquare, sumTriangle, countPairs, and countDuplicates. Key changes include:

1. sumSquare: Replaced nested loops with a direct computation, improving performance from O(n^2) to O(n).
2. sumTriangle: Utilized the triangular number formula to simplify the logic and reduce complexity.
3. countPairs: Implemented a counting array to efficiently count pairs, enhancing performance from O(n^2) to O(n).
4. countDuplicates: Streamlined the method to use a single loop, improving clarity and efficiency.

These enhancements improve both performance and readability, making the methods more suitable for larger datasets.