Catalog content provider doubles cache data in certain scenarios

Description

CatalogContentProvider uses the default content cache, but it also uses a cache in a lower layer, in CatalogContentLoader. This is because of a layering issue, where other parts that are technically in the layer below the cache benefit from caching.

This double caching works well in the in-memory scenario, because there are only two cache keys pointing to the same object instance. However other implementations, like a serializing cache, store double data.