Feature/kruskal mst

[prasanth-30011]

This PR adds an implementation of Kruskal’s Algorithm for computing the Minimum Spanning Tree (MST) of a weighted undirected graph, addressing Issue #7067.

✔ What’s Included

• Added KruskalMST.java under com.thealgorithms.greedyalgorithms
• Added a clean and efficient implementation using:
  • Greedy approach
  • Disjoint Set Union (Union-Find) with path compression
  • Edge class with comparable interface for sorting
• Added unit tests KruskalMSTTest.java that verify:
  • Correct MST weight for a sample connected graph
  • Correct handling of disconnected graphs (returns -1)

✔ Why This is Useful

• Kruskal’s Algorithm is a core greedy technique frequently used in:
  • Competitive programming
  • Graph theory education
  • Interview preparation
• Adds missing MST support to the greedy algorithms library
• Completes the request made in Issue #7067

🧪 Tests

All tests pass successfully using: