Feat/segment tree 2d

[YassaTalaat80]

Description

This PR adds a 2D Segment Tree (Tree of Trees) implementation to the datastructures/trees directory. It efficiently supports point updates and submatrix sum queries in O(log N * log M) time.

Checklist

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.50%. Comparing base (13aaad2) to head (fff95e6).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7363      +/-   ##
============================================
+ Coverage     79.46%   79.50%   +0.04%     
- Complexity     7131     7141      +10     
============================================
  Files           795      796       +1     
  Lines         23297    23358      +61     
  Branches       4587     4596       +9     
============================================
+ Hits          18513    18571      +58     
  Misses         4047     4047              
- Partials        737      740       +3     

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