QmlDesigner: Fix issues with Components and Repeaters

- Fixed state preview rendering by deparenting nodes under
  component wraps.
- Ensure state preview image is always clipped to root item.
  The state preview bounding box broke when Repeater was direct
  child of root and had delegate with rotation.
- Allow dragging items under Repeater to create implicit component.
- Allow dragging Components under Repeater.
- Do not ask for target property when Component is dragged under
  any node.
- Update nodeSource properly when reparenting implicit component
  or removing last child of a Component item.
- Fixed scene update when last child of a repeater is deleted/moved.

Fixes: QDS-5197
Change-Id: Iaaf1745e25db3522ffc1dba7fd1b051da29f5aec
Reviewed-by: Samuel Ghinet <samuel.ghinet@qt.io>
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

share/qtcreator/qml/qmlpuppet/qml2puppet/instances/objectnodeinstance.cpp

@@ -415,6 +415,16 @@ bool ObjectNodeInstance::isLockedInEditor() const
     return m_isLockedInEditor;
 }
 
+bool ObjectNodeInstance::isComponentWrap() const
+{
+    return m_isComponentWrap;
+}
+
+void ObjectNodeInstance::setComponentWrap(bool wrap)
+{
+    m_isComponentWrap = wrap;
+}
+
 void ObjectNodeInstance::setModifiedFlag(bool b)
 {
     m_isModified = b;
@@ -732,6 +742,10 @@ QObject *ObjectNodeInstance::createComponentWrap(const QString &nodeSource, cons
     QQmlComponent *component = new QQmlComponent(context->engine());
 
     QByteArray data(nodeSource.toUtf8());
+    if (data.isEmpty()) {
+        // Add a fake root element as an empty component is not valid and crashes in some cases
+        data.append("QtObject{}");
+    }
     data.prepend(importCode);
     component->setData(data, context->baseUrl().resolved(QUrl("createComponent.qml")));
     QObject *object = component;