Merge pull request #27988 from nklskyoy:attention-2-layer

AttentionOnnxAiLayer #27988 
 
Implements https://onnx.ai/onnx/operators/onnx__Attention.html#attention-23

### 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
- [ ] The PR is proposed to the proper branch
- [ ] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/dnn/include/opencv2/dnn/all_layers.hpp

@@ -1519,6 +1519,11 @@ CV__DNN_INLINE_NS_BEGIN
         static Ptr<RotaryEmbeddingLayer> create(const LayerParams &params);
     };
 
+    class CV_EXPORTS AttentionOnnxAiLayer : public Layer {
+     public:
+        static Ptr<AttentionOnnxAiLayer> create(const LayerParams &params);
+    };
+
     class CV_EXPORTS GroupNormLayer : public Layer {
     public:
         static Ptr<GroupNormLayer> create(const LayerParams &params);