Merge pull request #20367 from augustinmanecy:features2d-rw

**Merge with contrib**: https://github.com/opencv/opencv_contrib/pull/3003

### 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
- [ ] There is reference to 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.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/features2d/src/orb.cpp

@@ -666,6 +666,9 @@ public:
         scoreType(_scoreType), patchSize(_patchSize), fastThreshold(_fastThreshold)
     {}
 
+    void read( const FileNode& fn) CV_OVERRIDE;
+    void write( FileStorage& fs) const CV_OVERRIDE;
+
     void setMaxFeatures(int maxFeatures) CV_OVERRIDE { nfeatures = maxFeatures; }
     int getMaxFeatures() const CV_OVERRIDE { return nfeatures; }
 
@@ -717,6 +720,45 @@ protected:
     int fastThreshold;
 };
 
+void ORB_Impl::read( const FileNode& fn)
+{
+  // if node is empty, keep previous value
+  if (!fn["nfeatures"].empty())
+    fn["nfeatures"] >> nfeatures;
+  if (!fn["scaleFactor"].empty())
+    fn["scaleFactor"] >> scaleFactor;
+  if (!fn["nlevels"].empty())
+    fn["nlevels"] >> nlevels;
+  if (!fn["edgeThreshold"].empty())
+    fn["edgeThreshold"] >> edgeThreshold;
+  if (!fn["firstLevel"].empty())
+    fn["firstLevel"] >> firstLevel;
+  if (!fn["wta_k"].empty())
+    fn["wta_k"] >> wta_k;
+  if (!fn["scoreType"].empty())
+    fn["scoreType"] >> scoreType;
+  if (!fn["patchSize"].empty())
+    fn["patchSize"] >> patchSize;
+  if (!fn["fastThreshold"].empty())
+    fn["fastThreshold"] >> fastThreshold;
+}
+void ORB_Impl::write( FileStorage& fs) const
+{
+  if(fs.isOpened())
+  {
+    fs << "name" << getDefaultName();
+    fs << "nfeatures" << nfeatures;
+    fs << "scaleFactor" << scaleFactor;
+    fs << "nlevels" << nlevels;
+    fs << "edgeThreshold" << edgeThreshold;
+    fs << "firstLevel" << firstLevel;
+    fs << "wta_k" << wta_k;
+    fs << "scoreType" << scoreType;
+    fs << "patchSize" << patchSize;
+    fs << "fastThreshold" << fastThreshold;
+  }
+}
+
 int ORB_Impl::descriptorSize() const
 {
     return kBytes;