fix(core/graphcache): Add missing hasNext/stale flags to cached results

[kitten]

Summary

Ensures that the ssrExchange and Graphcache's cacheExchange don't accidentally remove hasNext (or stale) flags.

Set of changes

• Add hasNext passthrough to Graphcache
• Add hasNext passthrough to ssrExchange

[kitten]

cc @JoviDeCroock: Pretty trivial, so I went ahead and merged it.
On a side note, I was trying to actually make hasNext and stale required fields. We can still do that, but it'd mean updating like 50–100 lines of failing tests. Not a big deal, but we may want to check whether we really want to do this.
I think it's potentially worth it though.