Merge pull request #21066 from andrewerf:21052-openvino-native-onnx

Native ONNX to Inference Engine backend #21066

Resolves #21052

### 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 other license that is incompatible with OpenCV
- [x] The PR is proposed to proper branch
- [x] There is reference to original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
- [ ] The feature is well documented and sample code can be built with the project CMake

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

@@ -1021,14 +1021,14 @@ CV__DNN_INLINE_NS_BEGIN
       *                  * `*.pb` (TensorFlow, https://www.tensorflow.org/)
       *                  * `*.t7` | `*.net` (Torch, http://torch.ch/)
       *                  * `*.weights` (Darknet, https://pjreddie.com/darknet/)
-      *                  * `*.bin` (DLDT, https://software.intel.com/openvino-toolkit)
+      *                  * `*.bin` | `*.onnx` (OpenVINO, https://software.intel.com/openvino-toolkit)
       *                  * `*.onnx` (ONNX, https://onnx.ai/)
       * @param[in] config Text file contains network configuration. It could be a
       *                   file with the following extensions:
       *                  * `*.prototxt` (Caffe, http://caffe.berkeleyvision.org/)
       *                  * `*.pbtxt` (TensorFlow, https://www.tensorflow.org/)
       *                  * `*.cfg` (Darknet, https://pjreddie.com/darknet/)
-      *                  * `*.xml` (DLDT, https://software.intel.com/openvino-toolkit)
+      *                  * `*.xml` (OpenVINO, https://software.intel.com/openvino-toolkit)
       * @param[in] framework Explicit framework name tag to determine a format.
       * @returns Net object.
       *
@@ -1064,7 +1064,7 @@ CV__DNN_INLINE_NS_BEGIN
      *  backend.
      */
     CV_EXPORTS_W
-    Net readNetFromModelOptimizer(const String &xml, const String &bin);
+    Net readNetFromModelOptimizer(const String &xml, const String &bin = "");
 
     /** @brief Load a network from Intel's Model Optimizer intermediate representation.
      *  @param[in] bufferModelConfig Buffer contains XML configuration with network's topology.