network: improve gossip algorithm by ensuring duplicate messages aren't sent to peers

[noot]

currently, the gossip algorithm is flooding, so sending the message to every peer except the one that it was received from. this should be improved as to reduce network bandwidth. one method of improving the gossip mechanism is to choose a number of peers to send the message to, say n, then randomly select n peers out of our total peers. there are also other algorithms that could be used, will need some research and exploration. could make n configurable for now to determine best (ie. trade-off between bandwidth and propagation) value

[p4u]

Just in case this might help to get some ideas.

https://github.com/vocdoni/docs/wiki/SubPub-Mesh-routing

[noot]

this can be "pivoted" to be the gossiping of messages sent via notifications protocols

[noot]

also see spec 4.1.7.3: "Polkadot Host
implementers should implement a mechanism which only sends a transaction once to each peer and
avoids sending duplicates. Sending duplicate transactions might result in undefined consequences
such as being blocked for bad behavior by peers."

we need to ensure we aren't sending the duplicate messages to peers.