GROUP BY expr ASC|DESC has only noop implementation in tidb now

## Enhancement

```
SELECT *, MAX(id) mid FROM `users` GROUP BY user_id DESC
```

will show
```
[42000][1235] function GROUP BY expr ASC|DESC has only noop implementation in tidb now, use tidb_enable_noop_functions to enable these functions
```

But
```
SELECT *, MAX(id) mid FROM `users` GROUP BY user_id order by user_id DESC
```
is OK

so tidb could implement the short syntax