* Bump MaxPendingPayloads

* UnknownPayload error

* Improve ExchangeTransitionConfigurationV1 comment

* Extract MakeEmptyHeader

* Move MakeEmptyHeader to chain_makers

* Start with empty block as pending payload

* Only build payloads with the right parent hash

* Double check parent hash in SpawnMiningCreateBlockStage

* Simpler error formatting

* ReadHeadBlockHash instead of ReadHeadHeaderHash

* Avoid rebuilding already built blocks

* getPayload should stop the build process

* Tweaking stageLoopIsBusy

* Don't update pending payload after engine_getPayload