Add functionality to save inference images for the debugging purposes.

Save bmp images of inference results to /tmp as bmp files. BMP was
chosen to reduce encoding time. Saving is fully threaded. It can be
enable with qmake CONFIG+=save_images option

Also:
  - use antialised fonts in RKNN inference
  - moved class strings to inference base class
  - fixed silly segfault in ONNX inference
  - prevent writing results if class if exceeds valid values

Issue: https://denyspopov.atlassian.net/browse/AZ-38
Type: Improvement

misc/rtsp_ai_player/aiengineimagesaver.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#include <QThread>
+#include <QString>
+#include <opencv2/opencv.hpp>
+
+class AiEngineImageSaver : public QThread
+{
+    Q_OBJECT
+
+public:
+    AiEngineImageSaver(const cv::Mat &image, int imageNumber, QObject *parent = nullptr);
+    ~AiEngineImageSaver();
+
+protected:
+    void run() override;
+
+private:
+    cv::Mat image;
+    int imageNumber;
+};