[dataimport] dispatch and deprecate old code previously, the whole dataimport.py content has been copied in dataimport/__init__.py, then dataimport/importer.py API has been introduced. Following these changes, this cset: * dispatch __init__ code into sub-modules * dispatch unittest_dataimport accordingly * deprecates functions and classes that are deprecated by the new API Related to #5414753.

#!/usr/bin/env python
from cubicweb.cwctl import run
import sys
run(sys.argv[1:])