Automatically Mock user data for local test runs thoughout brainglobe

[alessandrofelder]

we store user data in a number of hidden folders. We want to be able to test that the user data works as expected without interfering with the local user data. A suggested solution for this exists in brainrender napari (mocking the home dir when running tests locally), but this can be reviewed and then expanded to cover all brainglobe napari plugin tests, as well as BrainGlobe workflows.