Review and update test cases to only constrain profiles/extensions (not direct resources)

Many of the existing tests are using resources rather than profiles for test StructureDefinitions. In many cases, the scope of the test means it shouldn't matter, but in the above case, it did. It might make some sense later on to maybe make the tests a little more "rigerous" by using the appropriate type of StructureDefinitions when testing things like rules. Now that custom resources and logical models are in the mix, it might be beneficial to ensure we are testing with objects that the rules are intended to operate on/with to prevent something from slipping the the cracks down the road.

_Originally posted by @joepaquette in https://github.com/FHIR/sushi/pull/802#discussion_r630455481_

Review the existing test cases that use resources rather than profiles or extensions for test StructureDefinitions. Start by identifying which tests exercise rules and replace only the test inputs whose scope requires profiles or extensions. Done means the relevant tests constrain the intended StructureDefinition types while continuing to pass, including coverage for custom resources and logical models where applicable.

Written by the indexing model from the issue text.