[zexoverz]

Description

Adds libp2p.listen(addrs) and libp2p.unlisten(addrs) so a node can start listening after start(), e.g. on <relay>/p2p-circuit once an app handshake with the relay is done. listen forwards to the transport manager. unlisten closes listeners whose requested or current address matches, so passing the same address you gave to listen works even for /tcp/0.

Closes #3645

Notes & open questions

Getting a relay reservation again after the relay drops is unlisten then listen. Happy to rename or move this if you'd rather it lived elsewhere.

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if necessary (this includes comments as well)
• I have added tests that prove my fix is effective or that my feature works

[zexoverz]

Could someone approve the workflow runs? They're at action_required, so CI hasn't run yet.