Support for CREATE TYPE

### CrateDB version

5.6.4

### CrateDB setup information

_No response_

### Problem description

I'm trying to replace postgres with CrateDB, but it seems CrateDB doesn't support creating types like postgres does, and our existing tables rely on a custom type.

### Steps to Reproduce

```sql
CREATE TYPE sort_key AS (
time timestamptz,
ident text
);
```

### Actual Result

`no viable alternative at input 'CREATE TYPE'`

### Expected Result

Should create the type