Add end-to-end test of multi-bucket indexing

[eddyashton]

While debugging something unrelated, I think I've spotted a bad branch in the sample logging app:

https://github.com/microsoft/CCF/blob/main/samples/apps/logging/logging.cpp#L1463-L1475

I think we should always be returning a next_link here, but that our current end-to-end tests don't hit the bug (full-history audit flows terminating early!) because they don't create sufficiently long ledgers. I noticed this while creating a novelly-long ledger to test long-lived forwarding. To create an end-to-end test for both of these, I think we finally need an app-specific configuration option, and a new e2e instance which starts a logging service with significantly reduced limits (smaller indexing buckets, quicker node-to-node key rotation) to test these edge cases.