NAT traversal: Use Testground for testing

[aarshkshah1992]

We should use Testground for testing QUIC & TCP hole punching.

This issue is to explore if it's possible and if it is, write solid tests that prove our approach works.

Quoting @raulk on some resources that can help achieve this:

Use Testground tarffic shaping https://docs.testground.ai/traffic-shaping And also the network package in the SDK: https://pkg.go.dev/github.com/testground/sdk-go@v0.2.5/network
Right now TG can do all traffic shaping that netlink allows us to do, plus simulate connected and disconnected scenarios, assign concrete IP addresses, etc.

[p-shahi]

closing in favor of libp2p/test-plans#64