DDL should report an error when creating a generated column with function "grouping"

[lcwangchao]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

> create table t(a int, b int as ((grouping(a))) stored);

2. What did you expect to see? (Required)

In MySQL, it reports an error:

mysql> create table t(a int, b int as ((grouping(a))) stored);
ERROR 1111 (HY000): Invalid use of group function

3. What did you see instead (Required)

mysql> create table t(a int, b int as ((grouping(a))) stored);
Query OK, 0 rows affected (0.09 sec)

4. What is your TiDB version? (Required)

master