Send the factory from the Wine host to the plugin

src/wine-host/bridges/vst3.h

@@ -83,4 +83,11 @@ class Vst3Bridge : public HostBridge {
      *       threads to exit.
      */
     Vst3Sockets<Win32Thread> sockets;
+
+    /**
+     * A plugin factory copied from the Windows VST3 plugin during
+     * initialization. The native VST3 plugin will request a copy of this
+     * information during its initialization.
+     */
+    std::unique_ptr<YaPluginFactory> plugin_factory;
 };