chore: Rename FileOfflineStore to DaskOfflineStore

[tokoko]

Fixes #3864

[shuchu]

lgtm

[franciscojavierarceo]

This PR may not have been ideal.

[franciscojavierarceo]

It's a breaking change is users are using File store in production, right?

[tokoko]

No, it shouldn't be. both file and dask in feature_store.yaml still refer to this offline store. Users generally never had to interact directly with the classes that were renamed (FileOfflineStore or FileOfflineStoreConfig).

[franciscojavierarceo]

Got it, it messed with the docs UI, so we can fix that. What was the reason behind this change? I think it makes it less obvious on how to use regular Files. I had a colleague who was new to Feast that was confused about it .

[tokoko]

The main reason was to drive home the distinction between DataSources and OfflineStores. Despite somewhat confusing naming, DataSource in feast is the concept that controls storage, while OfflineStore only controls computation engine. Sometimes those are closely linked together, but in this case not. Having FileOfflineStore doesn't make much sense as file system is not what's doing the computation, it's actually dask. FileSources can also be operated on by other offline store engines like duckdb and in the future spark, so calling dask engine FileOfflinStore was not consistent.

[franciscojavierarceo]

Yeah that makes sense. I think we probably need to update the documentation to clarify this.