[Sw eng] Add sim_ss_test_dict & lake_ss_test_dict to avoid DRY violations

[trentmc]

Background / motivation

predictoor_ss_test_dict() and similar have served me well, to avoid DRY violations.

For work in #779, I see that having sim_ss_test_dict & lake_ss_test_dict will avoid DRY violations there.

I am doing it as a separate PR, so that it's a simple well-contained refactoring.

TODOs / DoD

• Add sim_ss_test_dict, update tests
• Add lake_ss_test_dics, update tests