BlockProcessed is sent after a block has been processed and updated the state database.

ChainStarted is sent when enough validators are active to start proposing blocks.

Initialized is sent when the internal beacon node's state is ready to be accessed.

BlockProcessedData is the data sent with BlockProcessed events.

ChainStartedData is the data sent with ChainStarted events.

InitializedData is the data sent with Initialized events.

Notifier interface defines the methods of the service that provides state updates to consumers.