refactor(message): propagate highlight id instead of attrs

Problem:  Highlight group id is not propagated to the end of the message call
          stack, where ext_messages are emitted.
Solution: Refactor message functions to pass along highlight group id
          instead of attr id.

src/nvim/cmdhist.c

@@ -667,7 +667,7 @@ void ex_history(exarg_T *eap)
           } else {
             xstrlcpy(IObuff + len, hist[i].hisstr, (size_t)(IOSIZE - len));
           }
-          msg_outtrans(IObuff, 0);
+          msg_outtrans(IObuff, 0, false);
         }
         if (i == idx) {
           break;