qmllint: Warn about missing ListPropertyAssignBehavior

The behaviour of list properties in QML can be surprising. If we detect that a non-default list property has a binding set in a base type, and that in a derived type we assign another value to it, we should trigger a warning if no explicit ListPropertyAssignBehavior is set.

We should not do this for default properties, as this would trigger way too many warnings.

Compare https://doc.qt.io/qt-6/qtqml-documents-structure.html#listpropertyassignbehavior