Ordering issues in action queries

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Hi,

It seems that hasura actions are not preserving the original order of the json object received via REST endpoint.

For example, I'm using a REST server which returns a table with data already ordered by the field **total_count** (descending).
**total_count** is a computed field, **customer_idx** is a foreign key to the customer table.

## Query 1:
```gql
query {
get_customer_stats(ticket_filters: {}) {
total_count
customer_idx
}
}
```

Results are correctly ordered here by **total_count** (descending) as passed by the REST server:
```gql
{
"data": {
"get_customer_stats": [
{
"customer_idx": 2,
"total_count": 8
},
{
"customer_idx": 3,
"total_count": 5
},
{
"customer_idx": 1,
"total_count": 4
},
{
"customer_idx": 4,
"total_count": 1
}
}
}
```

## Query 2:
```gql
query {
get_customer_stats(ticket_filters: {}) {
total_count
customer_idx
customer {
name
}
}
}
```

Now hasura is changing the order of results, ordering by **customer_idx** (customer is a relationship to a foreign key):
```gql
{
"data": {
"get_customer_stats": [
{
"total_count": 4,
"customer_idx": 1,
"customer": {
"name": "Luigi Rossi"
}
},
{
"total_count": 8,
"customer_idx": 2,
"customer": {
"name": "Carlo Bianchi"
}
},
{
"total_count": 5,
"customer_idx": 3,
"customer": {
"name": "Mario Verdi"
}
},
{
"total_count": 1,
"customer_idx": 4,
"customer": {
"name": "Matteo Aranci"
}
}
}
}
```

## Other tests
- Ordering does not depend on the order of the fields in the query
- Ordering does not depend on any of the fields in the original table, only the one which the relationship is based on

Reproduce the two GraphQL queries against a Hasura action whose REST response is ordered and whose result includes a foreign-key relationship. Compare the returned list order with and without the nested customer selection; done means selecting the relationship no longer changes the upstream order.

Written by the indexing model from the issue text.