Support multiple data configs in evaluate

[athewsey]

Issue #, if available: #269

Description of changes:

Extend EvalAlgorithmInterface.evaluate() interface to support specifying a list of multiple data_config objects. evaluate() already returns a list of results by dataset, because when run with no data_config argument all applicable built-in datasets are analyzed. As mentioned in the attached issue, it was weird and confusing that users couldn't explicitly specify a set of more than one datasets to use.

Testing done:

• Added unit tests to cover all scenarios of get_dataset_configs()
• Added one integration test to validate multi-dataset functionality for the only evaluator (FactualKnowledge) where multiple integration test datasets had already been defined.

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[athewsey]

Rebased to current main. As I understood from the original review there wasn't actually a need for any change, but let me know if this is not the case!

Appreciate if y'all can help get this merged so we can have a more intuitive API 🙏