Merge pull request #25095 from cabelo:yolov8x

Added and tested yolov8x model #25095

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [X] I agree to contribute to the project under Apache 2 License.
- [X] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [X] The PR is proposed to the proper branch
- [X] There is a reference to the original bug report and related work
- [X] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [X] The feature is well documented and sample code can be built with the project CMake

Below is evidence of the test:
![opencv](https://github.com/opencv/opencv/assets/675645/40e81951-a8fd-410b-9dfc-c08254f99bdc)

samples/dnn/models.yml

@@ -18,6 +18,22 @@ opencv_fd:
   rgb: false
   sample: "object_detection"
 
+# YOLOv8 object detection family from ultralytics (https://github.com/ultralytics/ultralytics)
+# Might be used for all YOLOv8n YOLOv8s YOLOv8m YOLOv8l and YOLOv8x
+yolov8x:
+  load_info:
+    url: "https://huggingface.co/cabelo/yolov8/resolve/main/yolov8x.onnx?download=true"
+    sha1: "462f15d668c046d38e27d3df01fe8142dd004cb4"
+  model: "yolov8x.onnx"
+  mean: 0.0
+  scale: 0.00392
+  width: 640
+  height: 640
+  rgb: true
+  classes: "object_detection_classes_yolo.txt"
+  background_label_id: 0
+  sample: "yolo_detector"
+
 # YOLO4 object detection family from Darknet (https://github.com/AlexeyAB/darknet)
 # YOLO object detection family from Darknet (https://pjreddie.com/darknet/yolo/)
 # Might be used for all YOLOv2, TinyYolov2, YOLOv3, YOLOv4 and TinyYolov4