Consistently Use Simulator flag Helper methods in Campaign configurations

Merged John Derek Chapman requested to merge jchapman/athena:SimCoreTests_main into master

This merge request builds on !61433 (merged) and !61435 (merged) to make the configuration of simulation outside ISF behave in the same way in legacy and CA-based configuration. It is necessary to update this as some workflows, such as forward detector simulation are not supported inside ISF.

A new ART test is added to test this updated configuration syntax. The other jobs in SimCoreTests will be updated in a follow-up MR.

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