Allow setting `merge_with_nonprivate` in `run_experiment.py` command line params

[DonggeLiu]

Changes

Add arg: https://github.com/google/fuzzbench/blob/2bc06d4aca2c8dae20eeca47b95433ef543f99a8/experiment/run_experiment.py#L706

pass param: https://github.com/google/fuzzbench/blob/2bc06d4aca2c8dae20eeca47b95433ef543f99a8/experiment/run_experiment.py#L743

Update config: https://github.com/google/fuzzbench/blob/2bc06d4aca2c8dae20eeca47b95433ef543f99a8/experiment/run_experiment.py#L334

Reference links

It takes config file at: https://github.com/google/fuzzbench/blob/2bc06d4aca2c8dae20eeca47b95433ef543f99a8/experiment/run_experiment.py#L180C10-L180C31