expose peer information via rpc (#1362)

* expose peer information via rpc

* fixes tests

* cleanup

Co-Authored-By: xlc <xlchen1291@gmail.com>

* Update docs

Co-Authored-By: xlc <xlchen1291@gmail.com>

* Add missing docs

* keep original type for PeerInfo best_hash/best_number

* cleanup

* Update mod.rs

substrate/core/network/src/lib.rs

@@ -69,7 +69,7 @@ pub use protocol::{ProtocolStatus, PeerInfo, Context};
 pub use sync::{Status as SyncStatus, SyncState};
 pub use network_libp2p::{
     NodeIndex, ProtocolId, Severity, Protocol, Multiaddr,
-    obtain_private_key, multiaddr,
+    obtain_private_key, multiaddr, PeerId, PublicKey
 };
 pub use message::{generic as generic_message, RequestId, Status as StatusMessage};
 pub use error::Error;