webrtc/tests: Add libp2p-go to litep2p-perf to check webrtc

[lexnv]

The litep2p-perf crate is able to support litep2p server side:

• https://github.com/lexnv/litep2p-perf

We should extend the crate to spawn a libp2p-go client side over webrtc implementing the performance protocol:

• https://github.com/lexnv/litep2p-perf/blob/master/litep2p/src/perf.rs

Then we can have conformance tests to verify our substreams are not stalling and easily check the implementation is spec compliant with a battle-tested libp2p-go library.

• https://github.com/lexnv/litep2p-perf/blob/master/litep2p/src/perf.rs