Make YaPluginFactory abstract

And add separate implementations for the native plugin and the Wine
plugin host. This way we can easily allow the native host to do
callbacks without having to manage a load of lambdas.

src/plugin/vst3-plugin.cpp

@@ -17,6 +17,9 @@
 #include <public.sdk/source/main/pluginfactory.h>
 
 #include "bridges/vst3.h"
+// TODO: Remove include, instantiating and returning the `YaPluginFactory`
+//       should be done in `Vst3PluginBridge`
+#include "src/plugin/bridges/vst3-impls.h"
 
 #include <public.sdk/source/main/linuxmain.cpp>
 
@@ -87,8 +90,8 @@ SMTG_EXPORT_SYMBOL Steinberg::IPluginFactory* PLUGIN_API GetPluginFactory() {
     // TODO: Remove, this is just for type checking
     if (false) {
         boost::asio::local::stream_protocol::socket* socket;
-        YaPluginFactory* object;
-        write_object(*socket, *object);
+        YaPluginFactoryPluginImpl object(*bridge);
+        write_object(*socket, object);
     }
 
     if (!gPluginFactory) {