"Natural" ordering on functions doesn't work correctly in postgraphile v5
Version: postgraphile 5.0.0-beta.10

Issue: Ordering of a function does not match what is returned in SQL

Issue encountered in the following scenario:

The graphql query looks like this:

```
query SearchCustomers($query: String!, $sortByRecency: Boolean, $sortByAlphabetical: Boolean) {
 searchCustomers(searchquery: $query, sortbyrecency: $sortByRecency, sortbyalphabetical: $sortByAlphabetical) {
  nodes {
   ...CustomerFragment
  }
 }
}
```


The DB function that is being performed is as follows:
```
CREATE OR REPLACE FUNCTION public.search_customers(
    searchquery text,
    sortbyrecency boolean DEFAULT false,
    sortbyalphabetical boolean DEFAULT false)
    RETURNS SETOF customers 
    LANGUAGE 'sql'
    COST 100
    STABLE PARALLEL UNSAFE
    ROWS 50

AS $BODY$
WITH search_query AS (
    SELECT string_agg(trim(part) || ':*', ' & ') AS decorated_query
    FROM unnest(string_to_array(trim(searchquery), ' ')) AS part
), vs AS (
    SELECT 
        sca.*,
        ts_rank_cd(sca.document, to_tsquery(sq.decorated_query)) AS rank
    FROM 
        search_customer_accounts sca
        CROSS JOIN search_query sq
    WHERE
        sca.document @@ to_tsquery(sq.decorated_query)
    ORDER BY 
        rank DESC NULLS LAST
    LIMIT 50
)
SELECT 
    ca.*
FROM vs
LEFT JOIN customers ca ON ca.id = vs.customer_id
ORDER BY
    rank DESC NULLS LAST, 
    CASE 
        WHEN sortbyrecency = true THEN 
            ra.enrollment_date 
    END 
        DESC NULLS LAST,
    CASE 
        WHEN sortbyalphabetical = true THEN 
            ca.last_name || ca.first_name
    END 
        ASC NULLS LAST 
$BODY$;
```
If I run the query as is it will sort by the rank but in opposite order of what is done in the function. If I replace the following
```
ORDER BY
    rank DESC NULLS LAST, 
    CASE 
        WHEN sortbyrecency = true THEN 
            ra.enrollment_date 
    END 
        DESC NULLS LAST,
    CASE 
        WHEN sortbyalphabetical = true THEN 
            ca.last_name || ca.first_name
    END 
        ASC NULLS LAST 
```


with just
`ORDER BY ca.id DESC`


it will give me the customer list in the opposite ordering of what the function returns.

I went to try to add the orderBy flag to the query in Ruru and I don't see it. It likewise gave me this error when I tried it on the frontend:
```
[FAILED] GraphQL Document Validation failed with 1 errors;
[FAILED]   Error 0: Unknown argument "orderBy" on field "Query.searchCustomers".
```