[core] Node: Propagate attribute change via valueChanged signal

Propagate attribute value changes downstream using `valueChanged` signal
emission, instead of calling `_onAttributeChanged` directly.
This does not change the current core behavior, but it triggers the
property notification signal when in UI mode.
This makes changes happening upstream properly reflected in downstream nodes.

Author: yann-lty

meshroom/core/node.py

@@ -980,7 +980,7 @@ def _onAttributeChanged(self, attr: Attribute):
         if self.graph:
             # If we are in a graph, propagate the notification to the connected output attributes
             for edge in self.graph.outEdges(attr):
-                edge.dst.node._onAttributeChanged(edge.dst)
+                edge.dst.valueChanged.emit()
 
     def onAttributeClicked(self, attr):
         """ When an attribute is clicked, a specific function can be defined in the descriptor and be called.