Support for pagination when using relay pattern

**Describe the solution you'd like**
i would like the generated file to expose a function such as:
```
func queryPaged(
ctx context.Context,
client graphql.Client,
pageSize int,
pf func(T) error,
) error {
var cursor *string
resp, err := query(ctx, client, pageSize, cursor)
if err != nil {
return nil
}

for _, edge := range resp.X.Edges {
if err := pf(edge.GetNode()); err != nil {
return err
}
}
return nil
}
```
The issue I have is that this needs to be generated as the "X" is the query endpoint so it's not fixed.
One possibility is to add a generic method to the root query that returns the node inside "data",
Then we can write a generic pager with interfaces and generics.

**Describe alternatives you've considered**
Writing a pager function for every query, but that sort of defeats the purpose of the generator.

**Additional context**
The relay connection paging pattern is described here: https://relay.dev/graphql/connections.htm and here: https://graphql.org/learn/pagination/.

Start by tracing how the generated file exposes the root query and how the relay connection's query endpoint is represented. Review the relay pagination references and compare the proposed generic root-query method with the per-query pager alternative; done means generated clients support reusable pagination without requiring a separate pager for every query.

Written by the indexing model from the issue text.