sharding codec subchunk write order does not round-trip through pickling

[d-v-b]

the subchunk write order is not included in __getstate__. This should be a priority fix because otherwise sharding codecs will silently revert to the default write order when folks use dask.

[maxrjones]

@d-v-b was this fixed by #4008?

[d-v-b]

via #4011! closing