Add PaginatedKVStore traits upstreamed from ldk-server

Allows for a paginated KV store for more efficient listing of keys so
you don't need to fetch all at once. Uses monotonic counter or timestamp
to track the order of keys and allow for pagination. The traits are
largely just copy-pasted from ldk-server.

This also adds a PaginatedKVStoreSyncAdapter/PaginatedKVStoreAdapter so
you can use a paginated kv store in contexts that expect a regular key value store.

Adds some basic tests that were generated using claude code.

Author: benthecarman