Backwards Compatibility Testing

[gatesn]

We need some better infrastructure around how we guarantee backwards compatibility. We have lots of serialization formats, arrays, metadatas, dtypes, scalars, etc.

[robert3005]

We had metadata tests, in some cases they got disabled due to refactoring. Brining them back seems like a good first step to me. Probably whenever you make a change you need to persist every version of metadata and test them all

[robert3005]

There's compat gen job and we generate fixtures on every release, we could always take more fixtures