Like with FileStorage and fs1tools previously we were testing zodbtools/go only
with data generated by python2 and pickle protocol=2. However even on py2 there
are more pickle protocols that are in use, and also there is python3.

-> Modernize testdata generation to automatically pick up all ZODB kinds
   from recently-updated FileStorage/go testdata.

   Adjust tests on Go side to verify how zodbtools/go handle all generated zkinds.

All py2_pickle1, py2_pickle2, py2_pickle3 and py3_pickle3 are handled well out of the box.