feat(dot/telemetry): implement telemetry message network_state

[edwardmack]

Changes

• This implements telemetry message network_state.
• Part of network_state message contains connectedPeers field that contains:
  example data from polkadot node:

12D3KooWH4LX5TFftR1botGybbMQ8jWgUt5z1nToaxGsUdyiHARC":{
	"endpoint":{
		"dialing":"/ip4/135.181.214.98/tcp/30333"},
	"versionString":"Parity Polkadot/v0.9.3-aa3867609-x86_64-linux-gnu (SUBSTAR_io0)",
	"latestPingTime":{
		"secs":0,"nanos":335986866},
	"enabled":true,
	"open":true,
	"knownAddresses":["/ip4/135.181.214.98/tcp/30333"]},

however I don't know where to obtain this data (endpoint, versionString, latestPingTime, enabled, open, and knownAddresses

• Currently I'm reading data from s.host.peers (with Peers() method), which seems to give data from BlockAnnounceMsgType, is there a message type for getting peer info?

Tests

Issues

• related to Implement remaining telemetry messages #1501