fix(core): Set default hasNext for subscription results

[kitten]

Summary

Not all subscription transports have a built-in way of deduplicating subscriptions, since this may not be desireable. However, the presence of this in some transports has previously masked this issue.

The dedupExchange can prevent multiple identical operations. However, it backs off when a result comes in that has hasNext === false set.

The issue here is that subscriptionExchanges need to set hasNext to true by default for subscription operations to ensure that no duplicate subscriptions are triggered

Set of changes

• Set default hasNext field to true for subscriptions in makeResult