Lazily call `refreshTags` and `getExpiration`
When `"use cache"` is not used on the current route, we don't need to
call `refreshTags` for the configured cache handlers. So instead of
calling it at the beginning of the request for every cache handler, we
now call it lazily right before the first cache entry is retrieved for
the respective cache handler (once per request).
Similarly, we now call `getExpiration` for the implicit tags of the
current route lazily (also once per request) after an existing cache
entry has been retrieved, and its timestamp needs to be compared with
the expiration of the implicit tags.
