Update Dataset.__eq__ similarly, with tests about omnipy

[sveinugu]

This refers to the equality check of the Model class, tested here: https://github.com/fairtracks/omnipy/blob/da30c3c12bb260ee79419b7f78a4b2bf061f357b/tests/data/test_model.py#LL76C5-L76C18

Pydantic only checks the value when comparing equality of a BaseModel class, not differences in the model itself. Without this change in omnipy then Model[list[Any]]([123]) == Model[list[int]]([123]). However, we want `Modellist[Any] != Modellist[int]. This is now fixed for the Model class. This TODO is about fixing the same for the Dataset class (test-driven, so write the test first).

@pavelvazquez I think this is a good task for you to begin with while I am away.