Replace more instances new/delete with owning types (#4245)

* Use owning types when possible.

Note: the QByteArray s is detached to mimic previous behavior;
detach() guarantees that the QByteArray uniquely owns its data, since
otherwise it's COW. This may be relevant in case Plugin:instantiate
modifies s.data() -- this way the original QString is safe.

* Make m_filter a unique_ptr.

* Make m_activeRenderer a unique_ptr

* use std::string instead of strcpy + buffers

include/NotePlayHandle.h

@@ -26,6 +26,8 @@
 #ifndef NOTE_PLAY_HANDLE_H
 #define NOTE_PLAY_HANDLE_H
 
+#include <memory>
+
 #include "AtomicInt.h"
 #include "BasicFilters.h"
 #include "Note.h"
@@ -46,7 +48,7 @@ class EXPORT NotePlayHandle : public PlayHandle, public Note
 	MM_OPERATORS
 public:
 	void * m_pluginData;
-	BasicFilters<> * m_filter;
+	std::unique_ptr<BasicFilters<>> m_filter;
 
 	// specifies origin of NotePlayHandle
 	enum Origins

include/RenderManager.h

@@ -26,7 +26,7 @@
 #ifndef RENDER_MANAGER_H
 #define RENDER_MANAGER_H
 
-#include <vector>
+#include <memory>
 
 #include "ProjectRenderer.h"
 #include "OutputSettings.h"
@@ -70,7 +70,7 @@ private:
 	ProjectRenderer::ExportFileFormats m_format;
 	QString m_outputPath;
 
-	ProjectRenderer* m_activeRenderer;
+	std::unique_ptr<ProjectRenderer> m_activeRenderer;
 
 	QVector<Track*> m_tracksToRender;
 	QVector<Track*> m_unmuted;