BUG: Fix unnecessary confirmation popup after hovering over markups

When the mouse hovers over markups, active component (that is shown highlighted with different color) temporarily changes.
These changes also triggered MTime update in the display node, which resulted in unnecessary confirmation popups at scene close or exit.

Updated vtkMRMLMarkupsDisplayNode to invoke a modified event if active component is changed, but do not update its MTime to prevent unnecessary warning popups.

Modules/Loadable/Markups/MRML/vtkMRMLMarkupsDisplayNode.cxx

@@ -632,7 +632,9 @@ void vtkMRMLMarkupsDisplayNode::SetActiveComponent(int componentType, int compon
   }
   this->ActiveComponents[context].Index = componentIndex;
   this->ActiveComponents[context].Type = componentType;
-  this->Modified();
+  // Let observers know about node modification, but do not change the modified timestamp, as this is transient event
+  // (we do not want the application to display a warning popup on scene close exit if the mouse has hovered over a control point)
+  this->InvokeCustomModifiedEvent(vtkCommand::ModifiedEvent);
 }
 
 //---------------------------------------------------------------------------
@@ -785,7 +787,9 @@ int vtkMRMLMarkupsDisplayNode::UpdateActiveControlPointWorld(
 
   if (activeComponentChanged)
   {
-    this->Modified();
+    // Let observers know about node modification, but do not change the modified timestamp, as this is transient event
+    // (we do not want the application to display a warning popup on scene close exit if the mouse has hovered over a control point)
+    this->InvokeCustomModifiedEvent(vtkCommand::ModifiedEvent);
   }
 
   return controlPointIndex;