Improve validator-info CLI (#5121)

* Fix index OOB panic

* Handle 'get' empty validator-info responses properly

* Improve 'get' argument flow

* Improve arg help text

* Improve 'publish' argument flow

* Update book doc

client/src/rpc_client.rs

@@ -293,7 +293,6 @@ impl RpcClient {
                     format!("GetProgramAccounts parse failure: {:?}", err),
                 )
             })?;
-        println!("{:?}", accounts);
 
         let mut pubkey_accounts: Vec<(Pubkey, Account)> = Vec::new();
         for (string, account) in accounts.into_iter() {