Katana forking tracking

[kariy]

right now we're lacking tests on katana's forking feature. not much tests have been written for the forked storage provider.

the flow of the forked storage provider should generally be:

1. try to get the requested data from local storage
2. if not found, request from remote network
3. cache the result and return the value

need to write tests that ensure these steps are done correctly.

### Tasks
- [ ] better traces
- [ ] add metrics
- [ ] test if the caching system works
- [x] ensure 'not yet fetched' vs 'default' value is handled correctly ref #1850

[ScottyDavies]

hello @glihm can i hop on this?