Add systests for QUIC and routing discovery

[ivan4th]

Description

Presently there are no systests that validate QUIC protocol and routing discovery for libp2p. As a result, there may be unnoticed regressions from time to time, see libp2p/go-libp2p#2825 for instance (a fix for one such regression). We need systest cases for the following:

• QUIC protocol (WiP, need to have fewer extra test cases: #5902)
• relays, hole punching and routing discovery working together

The latter can be achieved by using multiple network namespaces simulating "a piece of WAN". Something like this can be found in libp2p tests (TODO: find the scripts, update this issue).

We're excluding libp2p from dependabot until these changes are implemented: #6018 Dependabot for libp2p libraries should be re-enabled once we have these tests in place.