Merge pull request #25357 from cabelo:yolov8m

Added and tested yolov8m model. #25357

### 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:
![yolov8m](https://github.com/opencv/opencv/assets/675645/f9bfe2c6-fe4a-42fc-93a6-17e4da5c9bb5)

samples/dnn/models.yml

@@ -62,7 +62,19 @@ yolov8n:
   background_label_id: 0
   sample: "yolo_detector"
 
-
+yolov8m:
+  load_info:
+    url: "https://github.com/CVHub520/X-AnyLabeling/releases/download/v0.1.0/yolov8m.onnx"
+    sha1: "656ffeb4f3b067bc30df956728b5f9c61a4cb090"
+  model: "yolov8m.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/)