To resolve undefined "Mat_to_vector_KeyPoint" error

Fix findContours crash for very large images (#7451)

* Cast step to size_t in order to avoid integer overflow when processing very large images

* Change assert to CV_Assert

  * add performance test for 32F and 64F threshold
  * requires update of opencv_extra

improved fix for java wrapper generator (gen_java.py) to avoid generation of java methods with duplicate signatures(v3)

Before:
    Ptr<Dictionary>((cv::aruco::Dictionary*)dictionary_nativeObj)
After:
    Ptr<cv::aruco::Dictionary>((cv::aruco::Dictionary*)dictionary_nativeObj)