feat: add self-balancing scapegoat tree implementation

[OmarAhmedTHE25th]

Description of Change

This PR adds a comprehensive implementation of a scapegoat tree, a self-balancing binary search tree. Unlike AVL or Red-Black trees, a scapegoat tree does not require extra storage (like height or color bits) per node, making it memory-efficient while still guaranteeing $O(\log n)$ amortized performance for basic operations.
Changes:
Self-Balancing Logic: Implemented find_traitor and restructure_subtree to handle α-weight balancing.
Modern C++
Features:
Added a custom iterator class for STL-compatible traversal.
Provided support for range-based for loops.
Advanced Queries: Added methods for kth_smallest, sum_in_range, and values_in_range.
Bulk Operations: Included insert_batch and delete_batch for efficient data handling.
Robust Testing: Included a comprehensive test suite in scapegoat_tests.cpp using assert() to verify tree properties and balancing after various operations.

Checklist

• Added description of change
• Added file name matches File name guidelines
• Added tests and example, test must pass
• Added documentation so that the program is self-explanatory and educational - Doxygen guidelines
• Relevant documentation/comments is changed or added
• PR title follows semantic commit guidelines
• Search previous suggestions before making a new one, as yours may be a duplicate.
• I acknowledge that all my contributions will be made under the project's license.

Notes:
A high-performance, self-balancing Scapegoat Tree implementation featuring STL-compatible iterators, amortized $O(\log n)$ operations, and α-weight balancing without per-node memory overhead.

[github-actions]

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[OmarAhmedTHE25th]

Hi! Just checking if any further changes are needed from my side. Happy to update if required. Thanks!