Add OFX plugin support and related infrastructure

This commit extends the OFX plugin support in Olive by:

- Initializing and scanning for OFX plugins
- Updating PluginNode to handle OFX plugin parameters and inputs
- Adding necessary methods and properties for OFX plugin integration
- Enhancing NodeFactory to include OFX plugin nodes
- Refactoring and renaming OliveInstance to OlivePluginInstance
- Introducing new classes for parameter handling (ParamInstance)
- Adding PluginJob for rendering OFX plugins
- Adjusting CMakeLists.txt files to include new source files

app/node/node.h

@@ -19,6 +19,8 @@
 #ifndef NODE_H
 #define NODE_H
 
+#include "ofxhImageEffectAPI.h"
+
 #include <map>
 #include <QMutex>
 #include <QObject>
@@ -1124,11 +1126,11 @@ public:
 
 	static const QString kEnabledInput;
 
-	std::shared_ptr<OFX::Host::ImageEffect::ImageEffectPlugin> getPlugin();
+	OFX::Host::ImageEffect::ImageEffectPlugin* getPlugin();
 protected:
 
 	// If is set, this is a plugin node.
-	std::shared_ptr<OFX::Host::ImageEffect::ImageEffectPlugin> plugin;
+	OFX::Host::ImageEffect::ImageEffectPlugin* plugin= nullptr;
 
 	void InsertInput(const QString &id, NodeValue::Type type,
 					 const QVariant &default_value, InputFlags flags,