Artemis: Refactor and Optimize Methods in the Double Class

[mike-turintech]

This pull request introduces significant optimizations and refactoring in the Double class. Key changes include:

1. Optimized the sumSquare method to reduce time complexity from O(n^2) to O(n) by removing nested loops.
2. Refined the sumTriangle method to improve efficiency from O(n^2) to O(n) by updating the loop range and using a direct formula.
3. Revised the countPairs method to utilize a HashMap for counting occurrences, enhancing performance from O(n^2) to O(n).
4. Simplified the countDuplicates method by eliminating unnecessary inner loops, improving clarity and efficiency.

Overall, these changes enhance performance and readability, aligning with best practices for code optimization.