Merge pull request #25810 from fengyuentau:python/fix_parsing_3d_mat_in_dnn

python: attempts to fix 3d mat parsing problem for dnn #25810

Fixes https://github.com/opencv/opencv/issues/25762 https://github.com/opencv/opencv/issues/23242
Relates https://github.com/opencv/opencv/issues/25763 https://github.com/opencv/opencv/issues/19091

Although `cv.Mat` has already been introduced to workaround this problem, people do not know it and it kind of leads to confusion with `numpy.array`. This patch adds a "switch" to turn off the auto multichannel feature when the API is from cv::dnn::Net (more specifically, `setInput`) and the parameter is of type `Mat`. This patch only leads to changes of three places in `pyopencv_generated_types_content.h`:

```.diff
static PyObject* pyopencv_cv_dnn_dnn_Net_setInput(PyObject* self, PyObject* py_args, PyObject* kw)
{
...
- pyopencv_to_safe(pyobj_blob, blob, ArgInfo("blob", 0)) &&
+ pyopencv_to_safe(pyobj_blob, blob, ArgInfo("blob", 8)) &&
...
}

// I guess we also need to change this as one-channel blob is expected for param
static PyObject* pyopencv_cv_dnn_dnn_Net_setParam(PyObject* self, PyObject* py_args, PyObject* kw)
{
...
- pyopencv_to_safe(pyobj_blob, blob, ArgInfo("blob", 0)) )
+ pyopencv_to_safe(pyobj_blob, blob, ArgInfo("blob", 8)) )
...
- pyopencv_to_safe(pyobj_blob, blob, ArgInfo("blob", 0)) )
+ pyopencv_to_safe(pyobj_blob, blob, ArgInfo("blob", 8)) )
...
}
```

Others are unchanged, e.g. `dnn_SegmentationModel` and stuff like that.

### 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

@@ -642,13 +642,13 @@ CV__DNN_INLINE_NS_BEGIN
          *  @param outputName name for layer which output is needed to get
          *  @details If @p outputName is empty, runs forward pass for the whole network.
          */
-        CV_WRAP void forward(OutputArrayOfArrays outputBlobs, const String& outputName = String());
+        CV_WRAP void forward(CV_ND OutputArrayOfArrays outputBlobs, const String& outputName = String());
 
         /** @brief Runs forward pass to compute outputs of layers listed in @p outBlobNames.
          *  @param outputBlobs contains blobs for first outputs of specified layers.
          *  @param outBlobNames names for layers which outputs are needed to get
          */
-        CV_WRAP void forward(OutputArrayOfArrays outputBlobs,
+        CV_WRAP void forward(CV_ND OutputArrayOfArrays outputBlobs,
                              const std::vector<String>& outBlobNames);
 
         /** @brief Runs forward pass to compute outputs of layers listed in @p outBlobNames.
@@ -727,7 +727,7 @@ CV__DNN_INLINE_NS_BEGIN
          *  as:
          * \f[input(n,c,h,w) = scalefactor \times (blob(n,c,h,w) - mean_c)\f]
          */
-        CV_WRAP void setInput(InputArray blob, const String& name = "",
+        CV_WRAP void setInput(CV_ND InputArray blob, const String& name = "",
                               double scalefactor = 1.0, const Scalar& mean = Scalar());
 
         /** @brief Sets the new value for the learned param of the layer.
@@ -738,8 +738,8 @@ CV__DNN_INLINE_NS_BEGIN
          *  @note If shape of the new blob differs from the previous shape,
          *  then the following forward pass may fail.
         */
-        CV_WRAP void setParam(int layer, int numParam, const Mat &blob);
-        CV_WRAP inline void setParam(const String& layerName, int numParam, const Mat &blob) { return setParam(getLayerId(layerName), numParam, blob); }
+        CV_WRAP void setParam(int layer, int numParam, CV_ND const Mat &blob);
+        CV_WRAP inline void setParam(const String& layerName, int numParam, CV_ND const Mat &blob) { return setParam(getLayerId(layerName), numParam, blob); }
 
         /** @brief Returns parameter blob of the layer.
          *  @param layer name or id of the layer.