message.c: add msg_echo_attr functions, use it for lua error messages

The added function behaves like the non-echo function but display message
in a echo-style way (i.e. tab and newline are preserved)

src/nvim/lua/executor.c

@@ -50,7 +50,7 @@ static void nlua_error(lua_State *const lstate, const char *const msg)
   size_t len;
   const char *const str = lua_tolstring(lstate, -1, &len);
 
-  emsgf(msg, (int)len, str);
+  emsgf_echo(msg, (int)len, str);
 
   lua_pop(lstate, 1);
 }