Refactor DM_Project_RandomForest.py for Python 3 and modern sklearn

[ZohaiAli]

This PR updates DM_Project_RandomForest.py in the following ways:

• Replace deprecated imports (cross_validation, grid_search) with model_selection
• Convert print statements to Python 3 style
• Structure code into functions for better readability
• Add error handling for missing files
• Use confusion matrix plotting and saving