ion-hash-python uses Ion Nature which was removed since ion-python 0.11.0

[cheqianh]

Ion Python 0.11.0 dropped the unnecessary factory method and classes such as Ion Nature for performance improvement. Ion Hash Python still uses Ion Nature, which should be dropped.

Currently uses versions that is earlier than 0.10.0 could block this issue.

As a long-term solution, we should drop Ion Nature in ion-hash-python, and have a testing mechanism to ensure that the ion-hash-python uses a desired version of ion-python and functions correct.