QWaylandWindow::doApplyConfigure called from the wrong thread

QWaylandWindow::setCanResize is called from the main thread and the render thread.

It then may call doApplyConfigure. doApplyConfigure uses mShellSurface which resides exclusively in the main thread.

It's not a trivial fix. A simple QMetaObject::invokeMethod won't suffice as potentially mCanResize could be true again by the time that gets handled in the main thread we don't want the event to get lost.

It's not just a hypothetical anymore as mentioned last meeting as we have a clear bug report downstream: https://bugs.kde.org/show_bug.cgi?id=450922