[VanillaBiometrics] Make some dask arguments visible in the CLI commands

Sometimes our heuristics that defines dask.bag.partition_size and n_workers is not enough to cover all range of problems. In this MR I'm adding the options --dask-partition-size and --dask-n-workers in the vanilla-biometrics CLI command, so that users can explicitly set, respectively, the dask bag partition size and the number of workers to start an experiment without having to play around with the API.