RPC: admin.peers() (#3960)

* RPC: admin.peers()

This RPC method returns information about the connected remote nodes.
https://geth.ethereum.org/docs/rpc/ns-admin#admin_peers

The peers are collected from all configured sentries.
See: https://github.com/ledgerwatch/interfaces/pull/102



Test with:
curl -X POST -H "Content-Type: application/json" --data '{"jsonrpc": "2.0", "method": "admin_peers", "params": [], "id":1}' localhost:8545

* save

* liner fix

Co-authored-by: alex.sharov <AskAlexSharov@gmail.com>