Currently, we cannot enable the feature flag for unique shard ids even in the all feature flag variants because the shard ref isn't used everywhere and so we trigger invariants when converting a shard ref containing a UUID into a shardId.

As a temporary solution to allow us to start testing, we will add resolution via the shard registry in the implicit shardRef -> shardId. This will allow us to test with unique ids enabled despite us not having finished the migration of types.