Add transport integration tests for circuitv2

[sukunrt]

We don't have integration tests for circuit v2 transport. It seems straightforward to add one.

We need to start an unlimited relay and use address factory to provide the right addresses from host.Addrs. Ideally, it should just work.

[badgooooor]

Hi, interested on working on this issue.

[rose2221]

would like to work on this

[p-shahi]

@rose2221 There is a closed PR here: https://github.com/libp2p/go-libp2p/pull/3162 picking up where badgor left off and addressing Sukun's comments would be a good place to start!