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/rtsp_ai_player.pro

@@ -16,9 +16,15 @@ else {
 }
 
 yolo_onnx {
+    message("Using YOLOv8 ONNX models for indoor testing.")
     QMAKE_CXXFLAGS += -DYOLO_ONNX
 }
 
+save_images {
+    message("Saving inference images to /tmp.")
+    QMAKE_CXXFLAGS += -DSAVE_IMAGES
+}
+
 opi5 {
     message("OPI5 build")
     CONFIG += link_pkgconfig