Also sync VST3 audio thread scheduling priorities

The exact same thing as the last commit, but for VST3 plugins.

src/plugin/bridges/vst3-impls/plugin-proxy.h

@@ -375,6 +375,13 @@ class Vst3PluginProxyImpl : public Vst3PluginProxy {
      */
     Steinberg::IPtr<Steinberg::FUnknown> host_context;
 
+    /**
+     * We'll periodically synchronize the Wine host's audio thread priority with
+     * that of the host. Since the overhead from doing so does add up, we'll
+     * only do this every once in a while.
+     */
+    time_t last_audio_thread_priority_synchronization = 0;
+
     /**
      * Used to assign unique identifiers to context menus created by
      * `IComponentHandler3::CreateContextMenu`.