QVulkanWindow: Force render on paint event

When a paint event is dispatched from the platform, application code
should redraw contents and submit a frame regardless of whether contents
have changed.

This fixes an issue where the window does not always update after being minimized on wayland, and would also be needed for non-composited X11 when exposure changes.

Pick-to: 6.9 6.8
Change-Id: I506872f439e0c16d71ad13def1c8b58a0491dd73
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
(cherry picked from commit d08f1d7dbc7b3fc23b81db1ded3314c1cf0dfeb2)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/gui/vulkan/qvulkanwindow.cpp

@@ -1552,6 +1552,7 @@ bool QVulkanWindow::event(QEvent *e)
     Q_D(QVulkanWindow);
 
     switch (e->type()) {
+    case QEvent::Paint:
     case QEvent::UpdateRequest:
         d->beginFrame();
         break;