Allow setting MLFlow experiment name through env var (#3266)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

ultralytics/yolo/utils/callbacks/mlflow.py

@@ -26,7 +26,7 @@ def on_pretrain_routine_end(trainer):
         mlflow_location = os.environ['MLFLOW_TRACKING_URI']  # "http://192.168.xxx.xxx:5000"
         mlflow.set_tracking_uri(mlflow_location)
 
-        experiment_name = trainer.args.project or '/Shared/YOLOv8'
+        experiment_name = os.environ.get('MLFLOW_EXPERIMENT') or trainer.args.project or '/Shared/YOLOv8'
         experiment = mlflow.get_experiment_by_name(experiment_name)
         if experiment is None:
             mlflow.create_experiment(experiment_name)