* Fix for Flow issues in SimpleCacheProvider
**what is the change?:**
- Fixed some flow errors which were somehow swallowed when CI
originally
- Loosen flow types to avoid issue with recursive loop in Flow; https://github.com/facebook/flow/issues/5870
**why make this change?:**
To unbreak master and unblock other changes we want to make.
**test plan:**
Flow passes!
**issue:**
https://github.com/facebook/react/issues/12941
* Fix lints
* [simple-cache-provider] Use LRU cache eviction
Max size is hard-coded to 500. In the future, we should make this
configurable per resource.
* Evict PAGE_SIZE records from cache when max limit is reached
Changes `createResource` to return an object with `read` and `preload`
methods. Future methods may include `set`, `subscribe`, `invalidate`,
and so on.
* [experimental] simple-cache-provider
Pushing an early version of this for testing and demonstration purposes.
* Change invariant to DEV-only warning
* Use function overloading for createResource type
Expresses that primitive keys do not require a hash function, but
non-primitive keys do.
* More tests
* Use export *
* Make Record type a disjoint union
* Pass miss argument separate from key to avoid a closure