Gui/CaptureOverlay: Work around Qt 6.11 being clever

Qt questionably tries to determine whether a QQuickItem has any children outside the bounds of the item that want to handle input. For the annotation toolbar, a popup is loaded later and so doesn't work for this check, so Qt thinks that it doesn't need to know about events outside its bounds.

This behaviour was introduced in qt/qt-declarative@81157314 and qt/qt-declarative@9efdc555.

To make sure that the annotations toolbar is not eligible for this 'optimisation', manufacture the conditions that would prevent it.

BUG: 515304
FIXED-IN: 6.6.4