Feature request: Support `collate` option on `orderByExpr`

**Is your feature request related to a problem? Please describe.**
I'd like to be able to provide a custom `COLLATE` in an `orderByExpr`

**Describe the solution you'd like**
Maybe
```ts
export type SerializedOrderByClause = {
column: string
direction?: `asc` | `desc` // omitted means 'asc'
nulls?: `first` | `last`
collate?: string
}
```

which would compile to something like
```sql
ORDER BY c COLLATE "de_DE";
```