Create multiple reporters from a single reporter instance when running simulations in batch

[JMorado]

Currently, when reporters are passed to run_production_batch, the output of all AlchemicalStates will be associated with the same output stream. This is not a problem if the states are run independently using run_single_state, as in this case each AlchemicalState has its own reporters, but when running simulations in batch it would be useful to find a way to create multiple reporters from a single reporter instance.