For log messages, demote the msg into the value

and make the type 'Log Message'.
This may just be a matter of personal taste, but I've always found these
messages-as-type super-confusing. I'd rather have some made up (but clear,
and thanks to the whitespace unlikely-to-otherwise-exist) type "Log Message".

This is also inline in what I've already done in the UI.

sentry/eventtypes/base.py

@@ -15,6 +15,6 @@ class DefaultEvent:
         )
 
         if message:
-            return truncatechars(message.splitlines()[0], 100), ""
+            return "Log Message", truncatechars(message.splitlines()[0], 100)
 
-        return "<unlabeled event>", ""
+        return "Log Message", "<no log message>"