DDL:check stored when alter column

[xiekeyi98]

What problem does this PR solve?

Fix #9453

What is changed and how it works?

When we exec ALTER TABLE ADD COLUMN, it will check it is stored column now.

Check List

Tests

• Manual test

mysql> create table t(a int );
Query OK, 0 rows affected (0.01 sec)

mysql> alter table t add column b int as (a+1) stored;
ERROR 1105 (HY000): unsupported add column
mysql> 

[xiekeyi98]

Close this PR because it is not ready in a short time.