Widget Designer: XML generated for QWebEngineView widgets cannot be used with CONFIG-=depend_includepath

Several of the widgets that can be used in the designer are implemented as custom widgets under the hood, e.g. QUndoView and QWebEngineView.

For QUndoView, the XML entry in the ui file is as follows:

<customwidget>
  <class>QUndoView</class>
  <extends>QListView</class>
  <header>QUndoView</header>
</customwidget>

For QWebEngineView, however, the generated XML is this:

<customwidget>
  <class>QWebEngineView</class>
  <header global="true>QtWebEngineWidgets/QWebEngineView</header>
</customwidget>

The important difference here is that the header path for QUndoView does not include the parent folder `QtWidgets` in which that header resides. This is significant when using the CONFIG-=depend_includepath option: For QUndoView it is sufficient to add DEPENDPATH+=$$[QT_INSTALL_HEADERS]/QtWidgets to work around QTBUG-74617. But for QWebEngineView one needs to add DEPENDPATH+=$$[QT_INSTALL_HEADERS] instead - which defeats the purpose of CONFIG-=depend_includepath.