Update Recon libp2p protocol to emit events about discovered peers

[nathanielc]

Description

Once #604 is finished this is about driving the sync of the peers ring with other peers. Concretely this will update the libp2p Recon behavior.

DOD

• The libp2p Recon behavior emits events when new peers are discovered
• These events can then be consumed by other behaviors (i.e. peer manager) to connect to the peers
• Events emitted should be enough for another behavior to add new peers and prune expired peers
• libp2p swarm test that shows events are emitted as expected