[dxvk] Add context method for WSI synchronization

Mostly convenience, but we do want to get rid of Begin/EndRecording
at some point.

src/dxvk/dxvk_context.h

@@ -78,6 +78,16 @@ namespace dxvk {
      */
     void flushCommandList(DxvkSubmitStatus* status);
 
+    /**
+     * \brief Synchronizes command list with WSI
+     *
+     * The next submission can be used to render
+     * to the swap chain image and present after.
+     */
+    void synchronizeWsi(PresenterSync sync) {
+      m_cmd->setWsiSemaphores(sync);
+    }
+
     /**
      * \brief Begins external rendering
      *