Adds zarr-specific data type classes. This replaces the internal use of numpy data types for zarr v2 and a fixed set of string enums for zarr v3. This change is largely internal, but it does change the type of the dtype and data_type fields on the ArrayV2Metadata and ArrayV3Metadata classes. It also changes the JSON metadata representation of the variable-length string data type, but the old metadata representation can still be used when reading arrays. The logic for automatically choosing the chunk encoding for a given data type has also changed, and this necessitated changes to the config API.

For more on this new feature, see the documentation