ProjectCacheWorker not flushing the cache

From https://gitlab.com/gitlab-org/gitlab-ce/issues/40107#note_47200904 I've noticed that we are not passing anything to flush the cache:

refresh_method_caches(types) receives no types, and we do types.each to find the things we would like to refresh.

This is called in several places as noted here https://gitlab.com/gitlab-org/gitlab-ce/issues/40107#note_50114719, but we'll have to look for all references and add the types or refactor the method if it makes sense.

If we are refreshing the cache by other means, we may want to rename ProjectCacheWorker to something like UpdateStatisticsWorker.