`SHOW CREATE` doesn't show indexes on virtual generated columns:

To reproduce:

```
create table t(a int primary key, b int generated always as (a*a), unique key (b));
show create table t;
```
Result:
```
+-------+------------------------------------------------------------------+
| Table | Create Table |
+-------+------------------------------------------------------------------+
| t | CREATE TABLE `t` ( |
| | `a` int NOT NULL, |
| | `b` int GENERATED ALWAYS AS ((`a` * `a`)), |
| | PRIMARY KEY (`a`) |
| | ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin |
+-------+------------------------------------------------------------------+
```
The index is present, and functions, as seen here:
```
> insert into t(a) values (2), (-2);
duplicate unique key given: [4]
```
But it is omitted from `SHOW CREATE` statements. This happens both in Dolt and in GMS.