Rename openssl-python to pyOpenSSL

[srittau]

Confusingly, if you pip install openssl-python you get a package pyopenssl. This project only had two release, the last one being in 2019. When you pip install pyOpenSSL you get a package OpenSSL, which is what our stubs have. This is a current project by the pyca. We should first merge #5645 to avoid merge conflicts.