Discovered during testing of MDL-67812 which adds a new repository.

We currently only have one cache for repositories, and it is defined as a per-request cache.
It stores several sets of prefixed data:

1. instance records (from the repository and repository_instances tables (cache keys prefixed with i:)
2. types by id (prefixed with types: or typesvis:)
3. types by name (prefixed with typename:)
4. all data (prefixed with all:)
5. options (prefixed with ops:)

In almost all of these cases they can be moved to an application cache, and some probably don't need to be stored in cache at all.

This should save activerepos * 2 DB reads on any page which uses a file picker.