Enable creating nodes behind a VPN

[p-shahi]

Done Criteria

It's possible to create a test-plan where a node is inside a VPN/all node traffic goes through the VPN tunnel.

Why Important

libp2p users/applications may run their nodes inside a VPN. Manual testing is possible today but not ideal.
Adding this feature will enable writing lightweight test-plans that serve as VPN environment regression tests.
Without it we can't guarantee new releases don't introduce regressions.
This will be useful for testing for/catching issues like: libp2p/go-libp2p#1849

User/Customer

libp2p implementers to test in different types of environments and give confidence to users/applications

Notes

Relates to: #1299, libp2p/test-plans#64