chainrpc: add chainkit RPC service

New endpoints: GetBlock, GetBestBlock, and GetBlockHash.

subrpcserver_config.go

@@ -217,6 +217,9 @@ func (s *subRPCServerConfigs) PopulateDependencies(cfg *Config,
 			subCfgValue.FieldByName("ChainNotifier").Set(
 				reflect.ValueOf(cc.ChainNotifier),
 			)
+			subCfgValue.FieldByName("Chain").Set(
+				reflect.ValueOf(cc.ChainIO),
+			)
 
 		case *invoicesrpc.Config:
 			subCfgValue := extractReflectValue(subCfg)