Future-proof Testing (Expansive protocol test coverage) 🧪

[p-shahi]

eta: 2023Q3

Why: Having interoperability tests with lots of transports, encryption mechanisms, and stream muxers is great. However, we need to stay backwards-compatible with legacy libp2p releases, with other libp2p implementations, and less advanced libp2p stacks.

Goal: Expand beyond unit tests and have expansive test-plan coverage that covers all protocols.

### Tasks
- [ ] https://github.com/libp2p/test-plans/issues/126
- [ ] https://github.com/libp2p/test-plans/issues/52
- [ ] https://github.com/libp2p/test-plans/issues/116
- [ ] https://github.com/libp2p/test-plans/issues/124
- [ ] GossipSub tests
- [ ] Kad DHT tests
- [ ] https://github.com/libp2p/test-plans/issues/195