Adds zarr-specific data type classes.
This change adds a ZDType base class for Zarr V2 and Zarr V3 data types. Child classes are
defined for each NumPy data type. Each child class defines routines for JSON serialization.
New data types can be created and registered dynamically.
Prior to this change, Zarr Python had two streams for handling data types. For Zarr V2 arrays, we used NumPy data type identifiers. For Zarr V3 arrays, we used a fixed set of string enums. Both of these systems proved hard to extend.
This change is largely internal, but it does change the type of the dtype and data_type
fields on the ArrayV2Metadata and ArrayV3Metadata classes. Previously, ArrayV2Metadata.dtype
was a NumPy dtype object, and ArrayV3Metadata.data_type was an internally-defined enum.
After this change, both ArrayV2Metadata.dtype and ArrayV3Metadata.data_type are instances of
ZDType. A NumPy data type can be generated from a ZDType via the ZDType.to_native_dtype()
method. The internally-defined Zarr V3 enum class is gone entirely, but the ZDType.to_json(zarr_format=3)
method can be used to generate either a string, or dictionary that has a string name field, that
represents the string value previously associated with that enum.
For more on this new feature, see the documentation