debug: add networkResponse endpoint with network identity

Author: dshulyak

proto/spacemesh/v1/debug.proto

@@ -9,6 +9,10 @@ import "google/protobuf/empty.proto";
 // They should not be used in production.
 service DebugService {
 
+    // NetworkInfo returns p2p network information. Mostly required for integration with deployment 
+    // and testing tooling.
+    rpc NetworkInfo(google.protobuf.Empty) returns (NetworkInfoResponse);
+
     // Accounts returns data for all the accounts currently in the node's current global state.
     // This includes each account's address, nonce and balance but excludes projection of account state.
     rpc Accounts (google.protobuf.Empty) returns (AccountsResponse);

proto/spacemesh/v1/debug_types.proto

@@ -6,4 +6,8 @@ import "spacemesh/v1/global_state_types.proto";
 
 message AccountsResponse {
     repeated Account account_wrapper = 1;
+}
+
+message NetworkInfoResponse {
+    string id = 1;
 }