Implement CachedVolume

[constantinpape]

Which cache do we use?
LRU cache?
Need general caching logic.

[constantinpape]

Also relevant https://zarr.readthedocs.io/en/stable/api/storage.html#zarr.storage.LRUStoreCache

cc @j6k4m8

[j6k4m8]

Yeah, agreed! I think it makes sense if adding another cache layer to stay flexible — it's possible that LRUCache makes sense for some workflows but not others. I'm imagining a "Proactive Cache" that caches the z+1 chunk when you request the zth chunk, or something...