Split logger.h into log_reader and log_writer

Much simpler!

Change-Id: I6c4ee363b56b67dac40c456261bbed79d01b8eb6
diff --git a/y2020/vision/BUILD b/y2020/vision/BUILD
index a58ed8c..a5d47fa 100644
--- a/y2020/vision/BUILD
+++ b/y2020/vision/BUILD
@@ -117,7 +117,7 @@
         ":vision_fbs",
         "//aos:init",
         "//aos/events:simulated_event_loop",
-        "//aos/events/logging:logger",
+        "//aos/events/logging:log_reader",
         "//third_party:opencv",
     ],
 )