For now this only checks that every entries in .tales are also in .values
so that .has_value works as expected. This also supports repairing the
structures with fixit argument.

We could check more, because there are other problems with proxy fields
internal structures:
 - sometimes some keys are in .values / .tales but not in .delegated_list
   this seem to happen after changing the target to a field of a different
   type, with different keys.
 - .delegated_list are not always sorted