Support XDG activation

QWaylandLayerShellIntegration has virtual hooks for Xdg Activation.

This is important to hook up in layer shell because activation using
requestActivate in Qt will go through this path. It also means we have
support for us to drop the implementation in KWindowSystem in favour of
calling into Qt.

src/qwaylandlayershellintegration.cpp

@@ -7,6 +7,7 @@
 
 #include "qwaylandlayershellintegration_p.h"
 #include "qwaylandlayersurface_p.h"
+#include "qwaylandxdgactivationv1_p.h"
 
 #include <QtWaylandClient/private/qwaylanddisplay_p.h>
 #include <QtWaylandClient/private/qwaylandwindow_p.h>
@@ -15,6 +16,7 @@ namespace LayerShellQt
 {
 QWaylandLayerShellIntegration::QWaylandLayerShellIntegration()
     : QWaylandShellIntegrationTemplate<QWaylandLayerShellIntegration>(4)
+    , m_xdgActivation(new QWaylandXdgActivationV1)
 {
 }