Add easy review tool for registered bootnodes on the DHT

[skunert]

After we have #1825, we should provide some tooling that allows to show the registered bootnodes on the DHT.

I imagine some CLI tool where I just specify the network, it then fetches the list of bootnodes form the relay chain and translates it via req-response protocol to the actual addresses of interest. Then it would just print a simple table. This could be useful for debugging and parachain node operators.

Up for debate: This could also be a subcommand of the node.

[MrishoLukamba]

I am up to take it, if it will be passed. And yes This will actually bring ease for debugging network-related issues, mostly on network topology

[eskimor]

Probably would make sense to make part of introspector .. so we have everything in one place? @alexggh @AndreiEres what do you think?

[alexggh]

Probably would make sense to make part of introspector .. so we have everything in one place? @alexggh @AndreiEres what do you think?

Yes, I think it could easily fit into the whois command here: https://github.com/paritytech/polkadot-introspector/blob/master/whois/README.md, till now we used this only for queries about validators, but I see no reason why it can't do the same for collators.