Storage update upon block import

The state diff is only updated on new shards. See `fn update_states(&self, header: &ParentchainHeader) -> Result<()>` https://github.com/integritee-network/worker/blob/3cc023423fafa93e806553b4ac0f2408c6a6ddbc/core-primitives/stf-executor/src/executor.rs#L168
Therefore, storage can only be updated for new shards.
Why is it not updated for every shard? 