Now we have difference between KisFilter::factoryConfguration() and
KisFilter::defaultConfiguration():

* KisFilter::factoryConfguration() creates an empty configuration
  object of a proper C++ type. This object should be filled by fromXML()
  right after this call.

* KisFilter::defaultConfiguration() calls factoryConfiguration() and
  fill it with default values at the state how they should look in
  filter dialog.

This split is needed, because new versions of Krita may introduce
options not available in older saves configs. In such cases, Krita
should be able to recognize if the config is the "old" one, and
doesn't have new parameters.

BUG:412982