cardano-cli: feeding ledger peers into genesis create-staked

[deepfire]

genesis create-staked needs to be extended with ability to inject stake pool -> IP/DNS address associations -- aka "ledger peers".

Suggested format interface: --ledger-peers PEERS-JSON-FILE, with the following structure:

{ public_key_1: ["ipaddr1", "ipaddr2", ...]
, public_key_2: ["dnsaddr3"]
, ...
}

It's not unlikely that this might need consensus integration as well.

Now -- where this information should go?

• the type path is: ShelleyGenesis -> ShelleyGenesisStaking -> PoolParams -> StakePoolRelay
• the relevant ledger code is at https://github.com/input-output-hk/cardano-ledger/blob/master/eras/shelley/impl/src/Cardano/Ledger/Shelley/PoolParams.hs#L220

[deepfire]

Suggested addition of DNS names support.

[deepfire]

Added the wherewithals of ledger peer placement.