feat(videoout): time the frame-limit wait as its own flip phase

The wait shows as frame_limit in the VideoOut.Flip timing, so a title held
by ANYPS5_FPS_LIMIT is told apart from one held by the vblank wait in the
trace and in the phases of the performance overlay's second page.

core/libs/prx/libSceVideoOut/src/VideoOutDriver.cpp

@@ -641,6 +641,7 @@ void VideoOutDriver::processFlip(FlipRequest& req) {
                 return;
             }
         }
+        timing.Mark("frame_limit");
         OnMainThread([&] { window.Ensure(req.width, req.height); });
         const auto extensions = windowExtensions(window.Handle());
         const AgcDriver::PresentationWindow target{window.Handle(), extensions, &createWindowSurface, &windowDrawableSize, req.width, req.height, req.timing};