Rewrite <Cache> element tests to not use cache()

Because we haven't decided on the client caching semantics of cache(),
we're going to remove the behavior for now and add it back later. So
we need to rewrite these client tests to not depend on cache(). This
essentially reverts the test suite back to what it was before facebook#25506.

There were also some tests in the ReactUse-test module that depended
on cache() too, which I've also updated.