Update port forwarding implementations

[jamesmcm]

Unfortunately Mullvad has disabled port forwarding.

So we should remove this code.

And also add port forwarding support for:

• ProtonVPN (we need to loop with natpmpc) - https://protonvpn.com/support/port-forwarding-manual-setup/
• AirVPN - https://airvpn.org/faq/port_forwarding/#:~:text=You%20can%20forward%20up%20to,listening%20program(s)%20settings.