Merge pull request #23319 from fengyuentau:fix_zoo_issue_136

Related issue: https://github.com/opencv/opencv_zoo/issues/136

Features added:

- Support operators with multiple output: ONNX Split.
- Support Slice without steps.

Bugs fixed:

- Wrong settings in ClipByValue (Relu6).
- Wrong calculation of pads in convolution layer (It is wrong generally but only fixed specifically for CANN for now).

### 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

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

@@ -347,11 +347,11 @@ CV__DNN_INLINE_NS_BEGIN
         /**
          * @brief Returns a CANN backend node
          *
-         * @param   inputsWrapper   layer inputs
-         * @param   index           layer id for op name
-         * @param   nodes           inputs of this node
+         * @param   inputsWrapper   input tensors of this CANN operator
+         * @param   nodes           nodes of input tensors
          */
-        virtual Ptr<BackendNode> initCann(const std::vector<Ptr<BackendWrapper> > &inputsWrapper, const int index, const std::vector<Ptr<BackendNode> >& nodes);
+        virtual Ptr<BackendNode> initCann(const std::vector<Ptr<BackendWrapper> > &inputsWrapper,
+                                          const std::vector<Ptr<BackendNode> >& nodes);
 
        /**
         * @brief Automatic Halide scheduling based on layer hyper-parameters.