Make the ogmios chain context performant

[nielstron]

I think to make the transaction building really performant I need instant access to chain tip, protocol parameters, epoch etc. Also UTxOs at an address should be as fast as possible, ideally cached.

To cover this, the context should be extended with two features

• async threads that keep chain tip, protocol parameters etc up to date
• a lock for the current state

The lock has this reasoning: When building a transaction, I want it to be built ASAP, no need to check the chain tip all the time. If the chain changes in a relevant way while building a transaction, the transaction is doomed anyways, so better be done fast with it. So during building a tx, lock the state including caching of utxos at addresses, locking the chain tip etc - make all accesses constant that can be made constant.