Refactor and remove deprecated notebooks for model training and serving

- Deleted `lecture4.train_register_basic_model.py` and `lecture4.train_register_custom_model.py` as they are no longer needed.
- Removed `lecture6.ab_testing.py` and `lecture6.deploy_model_serving_endpoint.py` to streamline the workflow.
- Consolidated A/B testing logic into a new `ab_testing.py` notebook for better organization.
- Merged model serving endpoint deployment into `deploy_model_serving_endpoint.py` for clarity.
- Created `marvel_create_monitoring_table.py` to handle monitoring table creation.
- Added `marvel_data_preprocessing.py` for data preprocessing tasks.
- Introduced `mlflow_experiment_tracking.py` for enhanced MLflow experiment tracking.
- Updated `train_register_basic_model.py` and `train_register_custom_model.py` to reflect new structure and practices.

Author: Jakee4488

notebooks/lecture6.ab_testing.py notebooks/ab_testing.pynotebooks/lecture6.ab_testing.py renamed to notebooks/ab_testing.py

@@ -28,7 +28,6 @@
 spark = SparkSession.builder.getOrCreate()
 
 filepath = "../data/marvel_characters_dataset.csv"
-
 # Load the data
 df = pd.read_csv(filepath)