Convert monotonic_remote_time to monotonic_clock::time_point

We were storing it as nanoseconds and casting all over.  Just save it as
a time_point.  There is no extra cost.

Change-Id: Icd53faa44036d9eafdcf7b117a8142d460c8c944
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/aos/events/logging/logfile_utils.h b/aos/events/logging/logfile_utils.h
index 4c82e4d..a42c6de 100644
--- a/aos/events/logging/logfile_utils.h
+++ b/aos/events/logging/logfile_utils.h
@@ -394,7 +394,7 @@
   // The local queue index.
   uint32_t queue_index = 0xffffffff;
 
-  std::optional<std::chrono::nanoseconds> monotonic_remote_time;
+  std::optional<aos::monotonic_clock::time_point> monotonic_remote_time;
 
   std::optional<realtime_clock::time_point> realtime_remote_time;
   std::optional<uint32_t> remote_queue_index;