Update prints to have which node they are from

This is enormously helpful when trying to debug the sorting flow.

Change-Id: Ia95acd3204d0ce241455805fc63f7886e88f014b
diff --git a/aos/events/logging/logfile_utils.h b/aos/events/logging/logfile_utils.h
index b1a2d67..23dadc8 100644
--- a/aos/events/logging/logfile_utils.h
+++ b/aos/events/logging/logfile_utils.h
@@ -342,6 +342,9 @@
   // And the index of the next file to open.
   size_t next_filename_index_ = 0;
 
+  // Node we are reading as.
+  const Node *target_node_ = nullptr;
+
   // Log file header to report.  This is a copy.
   FlatbufferVector<LogFileHeader> log_file_header_;
   // Current log file being read.
@@ -649,6 +652,10 @@
   std::vector<const Node *> nodes_;
 };
 
+// Returns the node name with a trailing space, or an empty string if we are on
+// a single node.
+std::string MaybeNodeName(const Node *);
+
 }  // namespace logger
 }  // namespace aos