dtype inference fails for platform-sensitive numpy data types

[d-v-b]

np.dtype('q') creates an instance of np.dtypes.LongLongDType which has a size depending on NumPy's compilation environment. In many cases np.dtypes.LongLongDType is a 64 bit integer, but this is not the same data type as np.dtypes.Int64DType and so it is rejected by zarr's Int64 dtype. We should make from_native_dtype more permissive in this case.

[d-v-b]

cc @maxrjones