CURA-4107
A newly created stack will have an empty definition changes container by
default, but when a machine or extruder gets activate, Cura will create
a definition changes container for it if it has an empty one. This lazy
creation caused the problem when after Cura creates a multi-extrusion
machine for the first time, switching to a different extruder tab will
cause an extruder stack change, which eventually triggers an unnecessary
auto-slice.
Except when we fill the instancecontainer via deserialising. Because then we want to retain the original version number.
Contributes to issue CURA-3427.
