Implement peerstore

[algoanne]

Problem

Algod needs to be able to keep track of data about hosts in the network. Peerstore is an interface in libp2p which provides methods for doing that, and will be required for using the swarm/dialer/host/network implementations in libp2p.

Solution

Add the ability for algod to construct a peerstore (populated with some mocked out peer info).

Lets look at both of the implementation currently in libp2p in memory and kv backed and see if one is better that the other in terms of how it integrates with persistence in #3004

Include documentation of our implementation (and especially how it differs from the standard).

[algoanne]

Some discussion:

libp2p has an implementation of the host interface, https://github.com/libp2p/go-libp2p/blob/master/p2p/host/basic/basic_host.go#L64 which gives us the node's peer ID and an in-mem peerstore. can we use this one?

For NewHost https://github.com/libp2p/go-libp2p/blob/master/p2p/host/basic/basic_host.go#L166C24-L166C31 you have to pass in a Network which is where it takes its Peerstore from.

a persistent peerstore constructor takes an ipfs datastore type https://github.com/libp2p/go-libp2p/blob/master/p2p/host/peerstore/pstoreds/peerstore.go#L13. And I think this is what we want to use instead of the in-memory peerstore. There are several implementations of the go-datastore that we can use, https://github.com/ipfs. For the POC, I'll use leveldb.