Cardano Updates

async_trait seems to work well until we have async traits in stable generally.

Preparation for disk storage which will require async in #9

Avoid problem using block number for sequencing when rollback affects it

Closes #13

Note that there is now no default for publish-utxo-deltas-topic

Need to do the same for both Alonzo and Conway types - seems no way round this in the Pallas structure.

Not yet used in messages.  Note both UTXO and new Certificates messages should become optional.

In advance of adding methods to start and end blocks
so we can batch up the deltas into a single message per block

All messages now pass around Address structures which define the full address.

Note the map from Pallas to our Address is currently just on TxUnpacker (with a simple Byron-only version in GenesisBootstrapper) - this is to avoid messages / common being dependent on Pallas as well.

Going forward this should be the rule - messages should not use anything external except for Caryatid.

Saves downstream modules from needing Pallas to decode them.

Needs work - a full description of an address has multiple hashes (payment, staking, script) - should be a module in
'common' and messages should depend on it.

In particular this won't work for address deltas at the moment because the TxUnpacker assumes they are all Payment, where was the GenesisBoostrapper (rightly) assumes they are Byron.

In preparation for it having more state and complexity

Only sends payment address messages and doesn't unpack the addresses yet

Preparation for sending address delta messages

Also fix some tests broken by volatile index changes

Store indexes of volatile blocks with created/spent UTXOs.