Add IAudioProcessor instance to ComponentInstance

So we don't have to these expensive casts every time.

src/wine-host/bridges/vst3.cpp

@@ -26,7 +26,7 @@ ComponentInstance::ComponentInstance() {}
 
 ComponentInstance::ComponentInstance(
     Steinberg::IPtr<Steinberg::Vst::IComponent> component)
-    : component(component) {}
+    : component(component), audio_processor(component) {}
 
 Vst3Bridge::Vst3Bridge(MainContext& main_context,
                        std::string plugin_dll_path,

src/wine-host/bridges/vst3.h

@@ -49,7 +49,7 @@ struct ComponentInstance {
     // All smart pointers below are created from `component`. They will be null
     // pointers if `component` did not implement the interface.
 
-    // TODO: Implement things like `IConnectionPoint` and `IAudioProcessor`
+    Steinberg::FUnknownPtr<Steinberg::Vst::IAudioProcessor> audio_processor;
 };
 
 /**