Moved binary from the package root directory to python-X.Y

[asenyaev]

• Moved a binary (.so / .pyd) from cv2/ folder in a package to cv2/python-X.Y.
• Added an overwriting for config.py file instead of config-X.Y.py, because we have a proper path to our binary in config-X.Y.py file, but config.py doesn't have a proper path to other binaries (e.g. the path is to /lib64 in a docker container)
• Added 3.4 branch for builds in Pull Requests in case of we have different setup.py files

[asenyaev]

I will update opencv submodule after merging https://github.com/opencv/opencv/pull/21209 to start actions.

Upd. Decided to keep imports for opencv-python in this repo.