Invisible Columns

Support things like this:
```sql
CREATE TABLE t1(
id int PRIMARY KEY,
c1 int INVISIBLE
);
```

This is useful for:
- A part of Generated Invisible Primary Keys (GIPK) ( https://dev.mysql.com/doc/refman/8.4/en/create-table-gipks.html )
- Indexes on generated columns that are hidden. To have functional indexes with breaking `INSERT` and `SELECT` where the column list isn't supplied.