Pagination: support cache policy for initial fetch

[pondorasti]

Use case

I would like to be able to leverage the normalized cache when using AsyncGraphQLQueryPager and pull data from cache without triggering a new fetch request.

Describe the solution you'd like

The private implementation of fetch as part of the AsyncGraphQLQueryPager already supports setting cachePolicy. I would like the same functionality to be extended to the public version of fetch:

-  func fetch() async {
+  func fetch(cachePolicy: CachePolicy = .returnCacheDataAndFetch) async {
    reset()
    await fetch(cachePolicy: cachePolicy)
  }

[github-actions]

Do you have any feedback for the maintainers? Please tell us by taking a one-minute survey. Your responses will help us understand Apollo iOS usage and allow us to serve you better.