WIP: Adding snapshot with V0 to data-regression

I think i need to add another factset to the repo before attempting another snapshot with the latest version, so that we can have a snapshot that is built incrementally from one with the old metadata and generates a new snapshot with the new metadata
I could probably use some feedback on how to tidy this test up,

For one, i'm pretty sure the `VirtualDictionaryWindow` is overkill for the bits that i need out of it, would `dict: Dictionary` work in its place?