feat: openvpn + wireguard experiments

[ainghazal]

Checklist

• [x] I have read the contribution guidelines
• [ ] reference issue for this pull request:
• [ ] if you changed anything related how experiments work and you need to reflect these changes in the ooni/spec repository, please link to the related ooni/spec pull request:

Description

First iteration of openvpn + wireguard experiments.

This is still a work in progress, publishing now so that others can replicate experiments.

[ainghazal]

I am publishing this branch early on to be able to receive feedback. Tests are not there yet, and I'm still working in a better way to distribute endpoints and credentials.

The openvpn experiment can be replicated with, for instance, the files on this gist.