Feat: store-or-network in Relay Modern stable

Relay experimental has the option to use `store-or-network` as it's fetch policy (which only fetches if the data is not in the store)

However, relay v9 only has a `store-and-network` that will always refetch the data regardless of if it's in the store.

Would it be possible to bring the `store-or-network` option into the stable releases of Relay Modern?

The alternative options the currently exist don't appear to be a suitable replacement for `store-or-network`.

[relay-query-lookup-renderer](https://github.com/relay-tools/relay-query-lookup-renderer) doesn't cache in-progress promises resulting in [duplicate network requests](https://github.com/relay-tools/relay-query-lookup-renderer/issues/26) for the same data.

[ReactRelayLocalQueryRenderer](https://github.com/facebook/relay/blob/master/packages/react-relay/ReactRelayLocalQueryRenderer.js) won't do a network request if the data is not found.