Update tests to use local data/metadata where possible

[edwardchalstrey1]

Update test files to use local data (See comment: https://github.com/alan-turing-institute/scivision/pull/75#discussion_r753133735)

• [ ] update tests/test_dataset_scivision.yml (intake config) to link to a real local dataset and test attributes of the loaded intake object, or that it can be converted to xarray or numpy
• [ ] update tests/test_model_scivision.yml so it loads a locally stored model from within scivision repo