Support for syncing on mergemock (#3174)

* block proposing

* standard finalized

* mergemock execution

* private chain can now be ran yay

* perfectioned

* polished

* more polishing

* resize PR

* resize PR

* resize PR

* simplifications

* fixed tests

* better syncronous communication

* better syncronous once again

* clean

* Re-enabled headers verification

* mining finish

* mining finish

* cleaned hash computation

* fixed evm bug

* go.mod

* Update .gitignore

* Update .gitignore

* Update .gitignore

* removed new line from .gitignore

* added go.mod and go.sum

* feeRecipient into preset

* useExternal

* todo

* fixed comment for forkchoiceUpdateV1

* smaller

* smaller

* Revert changes to miner frequency

* Restore useExternalTx

* Fix headerLoadFunc

* do not reset payloadId

* rename

* extra is empty

Co-authored-by: yperbasis <andrey.ashikhmin@gmail.com>