Refactor Lazy and Eager Prim's MST implementations

[williamfiset]

Summary

• Add Javadoc explaining lazy vs eager approaches, time/space complexity
• Use Integer.compare() instead of subtraction in compareTo() to avoid overflow
• Apply single-line body formatting rule throughout
• Trim the indexed priority queue in EagerPrims to only the operations needed by the algorithm (removed size, pollMinKeyIndex, valueOf, update, increase, toString, isMinHeap, and validation helpers)
• Consolidate duplicated print logic into printMst helper, fix "No MST does not exists" typo
• Clean up examples: rename for clarity, remove benchmark and duplicate slide examples
• Add JUnit 5 tests for both LazyPrims (13 tests) and EagerPrims (14 tests), including a lazy-vs-eager agreement test

Test plan

• bazel test //src/test/java/com/williamfiset/algorithms/graphtheory:LazyPrimsAdjacencyListTest — 13 tests pass
• bazel test //src/test/java/com/williamfiset/algorithms/graphtheory:EagerPrimsAdjacencyListTest — 14 tests pass

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