Add unit tests for graph algorithms (BFS, DFS, Dijkstra, Bellman-Ford…

[prashantdubeypng]

…) #7133

• Created BellmanFordTest.java with 10 test methods covering various graph scenarios

• Created ConnectedComponentTest.java with 15 test methods for DFS-based component counting

• Enhanced MatrixGraphsTest.java with additional BFS/DFS test cases

• Enhanced DijkstraAlgorithmTest.java with comprehensive shortest path tests

Fixes #7133

• 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 78.87%. Comparing base (316def4) to head (3fe62da).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7152      +/-   ##
============================================
+ Coverage     78.62%   78.87%   +0.25%     
- Complexity     6825     6828       +3     
============================================
  Files           766      766              
  Lines         22607    22607              
  Branches       4444     4444              
============================================
+ Hits          17774    17831      +57     
+ Misses         4119     4064      -55     
+ Partials        714      712       -2     

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