Add unit tests for the two main keyframing API functions: `insert_key_rna()` and `insert_keyframe()`.
The tests are not exhaustive of every possible permutation of parameters, but the tests do try to hit each of the behaviors in at least one permutation. In the future tests should also be added for the lower-level keying functions and behaviors as well, but I'm leaving that as future work since we aren't changing/refactoring those functions right now.
Pull Request: https://projects.blender.org/blender/blender/pulls/122553
b9c7e5e766