Implement WebRTC-Direct for nodejs

[EliasOenal]

libp2p/js-libp2p#2583
libp2p/js-libp2p#2581

These were closed a while ago and now libp2p should support this even on nodejs. Make sure WebRTC is fully enabled with as much of its featureset as possible, on nodejs, as well as in the browser. If possible on the platform, also enable the maximum connectivity, via NAT traversal, etc. Find out what we have and look up how much more is possible. If there are missing improvements, implement them and add tests. This feature is critical for Verity, as it will allow web nodes hosted on HTTPS to connect to others without a signed certificate. (WebRTC supports self-signed)

[victorhahncastell]

Hey Copilot, your end-to-end tests in test/core/networking/webrtc_direct_e2e.test.ts are not proper Verity end-to-end tests as they test direct library invocation rather than our code. Please scrap those tests and re-write them. For guidance, look e.g. at test/core/e2e/notify.test.ts. The tests should spawn full Verity nodes by constructing CoreNode objects.

(No need to check for isNode in your tests, unit tests will only ever be run on NodeJS.)