Call frameRendered for undamaged Wayland surfaces

Currently, if a Wayland surface registers a frame callback but does
not send a damage event, the callback will not be serviced even after
KWin has completed a compositing cycle and is therefore ready to
render a new frame for the surface. Since some clients, including any
using NVIDIA's Wayland EGL implementation, wait for frame events
before preparing each frame this behavior can result in hangs if a
compositing cycle occurs between registering the frame callback and
sending the damage event.

Instead, in accordance with the Wayland specification, frame callbacks
should be serviced (via KWayland::Server::SurfaceInterface::frameRendered)
for all visible windows - not just those damaged since the last
compositing cycle.

composite.cpp

@@ -764,7 +764,7 @@ void Compositor::performCompositing()
     m_timeSinceStart += m_timeSinceLastVBlank;
 
     if (waylandServer()) {
-        for (Toplevel *win : qAsConst(damaged)) {
+        for (Toplevel *win : qAsConst(windows)) {
             if (auto surface = win->surface()) {
                 surface->frameRendered(m_timeSinceStart);
             }