System information (version)

• OpenCV => 4.x
• Operating System / Platform => Any
• Compiler => Any

Detailed description

According to official documentation, OpenVino supports reading native ONNX models since 2020.4 release. I suppose it's worth it to add this feature to OpenCV DNN module.
I'd be glad to submit PR after discussing the preferred interface.

Issue submission checklist

• I report the issue, it's not a question
• I checked the problem with documentation, FAQ, open issues,
  forum.opencv.org, Stack Overflow, etc and have not found solution
• I updated to latest OpenCV version and the issue is still there
• There is reproducer code and related data files: videos, images, onnx, etc