[ui] AttributeEditor: remove SortFilterDelegateModel

Usage of DelegateModel for model filtering has not proven to be the most stable solution, and might be responsible for random crashes happening during engine's garbage collection.  Implement Loader-based alternative:
* first delegate is a Loader which creates the AttributeItemDelegate if necessary
* compensate spacing using negative height when element is hidden

meshroom/ui/qml/GraphEditor/AttributeEditor.qml

@@ -19,31 +19,25 @@ ListView {
 
     implicitHeight: contentHeight
 
-    clip: true
     spacing: 2
+    clip: true
     ScrollBar.vertical: ScrollBar { id: scrollBar }
 
-    model: SortFilterDelegateModel {
-
     model: attributes
-        filterRole: GraphEditorSettings.showAdvancedAttributes ? "" : "advanced"
-        filterValue: false
 
-        function modelData(item, roleName) {
+    delegate: Loader {
-            return item.model.object.desc[roleName]
+        active: !object.desc.advanced || GraphEditorSettings.showAdvancedAttributes
-        }
+        visible: active
+        height: item ? item.implicitHeight : -spacing // compensate for spacing if item is hidden
 
-        Component {
+        sourceComponent: AttributeItemDelegate {
-            id: delegateComponent
+            width: root.width - scrollBar.width
-            AttributeItemDelegate {
-                width: ListView.view.width - scrollBar.width
             readOnly: root.readOnly
             labelWidth: root.labelWidth
             attribute: object
             onDoubleClicked: root.attributeDoubleClicked(mouse, attr)
         }
     }
-    }
 
     // Helper MouseArea to lose edit/activeFocus
     // when clicking on the background