feat: add Centroid Decomposition of a tree

[binarymind-dev]

Description

Adds Centroid Decomposition implementation to the graph/ directory.

Algorithm

Centroid Decomposition decomposes a tree by recursively finding
and removing centroids, creating a centroid tree of depth O(log N).
Used for efficient path queries on trees.

Complexity

• Preprocessing: O(N log N)
• Space: O(N)

Tests

• Centroid parent structure on a path graph
• Count paths of length 2 in a star graph
• Count paths of length 2 in a path graph
• Count edges (paths of length 1)
• Single node edge case

Closes #(issue number if any)

[binarymind-dev]

Hi @Panquesito7 and @realstealthninja,

Could you please approve the workflows so the CI checks can run for this PR?
I've followed the contribution guidelines. Thank you! 🙏

[github-actions]

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