`experiment_builder.create_experiment` often gets extra unused kwargs

[lebrice]

This is related to #968 , where we uncovered that create_experiment is/was often ignoring some extra keyword arguments.
As part of #968, these extra kwargs are not silently ignored anymore, and a warning-level logging message is raised instead.

We might have to watch out that this warning doesn't appear too frequently in normal user code.

It might be preferable to remove the **kwargs (and the warning) entirely, or some other solution.