Improve log_cats raw and fetching capabilities

Make --raw be able to print parsed messages.  Much more useful than just
the headers.

Also, let --fetch control if we print out messages from before the start
of the log file.

Change-Id: I150bad1d5ac5b3caa7f5cab6ff6fe5cb7b4a7f67
diff --git a/aos/configuration.cc b/aos/configuration.cc
index cef3876..43e44f2 100644
--- a/aos/configuration.cc
+++ b/aos/configuration.cc
@@ -12,6 +12,7 @@
 #include <string_view>
 
 #include "absl/container/btree_set.h"
+#include "absl/strings/str_cat.h"
 #include "aos/configuration_generated.h"
 #include "aos/flatbuffer_merge.h"
 #include "aos/json_to_flatbuffer.h"
@@ -539,6 +540,12 @@
   return FlatbufferToJson(cleaned_channel);
 }
 
+std::string StrippedChannelToString(const Channel *channel) {
+  return absl::StrCat("{ \"name\": \"", channel->name()->string_view(),
+                      "\", \"type\": \"", channel->type()->string_view(),
+                      "\" }");
+}
+
 FlatbufferDetachedBuffer<Configuration> MergeConfiguration(
     const Flatbuffer<Configuration> &config,
     const std::vector<aos::FlatbufferString<reflection::Schema>> &schemas) {