Merged requested to merge jchapman/athena:CollectionMerger_main into master
For the CA-based configuration, this is just switching to use the
usesFatras() method rather than comparing to a list of simulator names.
For the legacy configuration, the list of input collection names for each subsystem is now sorted. (Previously the order differed in legacy and CA-based configuration which could give differing output when the collections were merged.)