As promised in 6c162438 (go/zodb: Draft support for Map and List) add
test that Map and List implemented on Go side can load PersistentMapping
and PersistentList data generated by Python.

Test that Py side can load Map and List data generated by Go is still pending.

Testdata is still generated with zodbtools f9d36ba7~ i.e. before
nexedi/zodbtools!29 was merged.