hive: ethereum/consensus: need to port header validation code

[jangko]

the number of failing cases in ethereum/consensus test suite dwindling to 59.
one case (bcHomesteadToEIP150/EIP150Transition_HomesteadToEIP150At5) identified to be caused by a subtle bug in mapper.jq file. (#667)
but majority of them related to block header validation.

sub category such as bcTotalDifficultyTest and bcInvalidHeaderTest clearly indicate we need to port those validation code
from test_blockchain_json back to nimbus.

related procs in test_blockchain_json:

func validateGasLimit(gasLimit, parentGasLimit: GasInt)
proc validateHeader(header, parentHeader: BlockHeader, checkSeal: bool)
func validateUncle(currBlock, uncle, uncleParent: BlockHeader)
proc validateGasLimit(chainDB: BaseChainDB, header: BlockHeader)
proc validateUncles(chainDB: BaseChainDB, currBlock: EthBlock, checkSeal: bool)
func isGenesis(currBlock: EthBlock): bool
proc validateBlock(chainDB: BaseChainDB, currBlock: EthBlock, checkSeal: bool): bool

bcMultiChainTest sub category also pass test_blockchain_json, I suspect we also need to port some code back to nimbus but not sure which part.

after the ported code is stable enough, we can remove those in test_blockchain_json

[jangko]

after #668, failing test cases reduced again from 59 to 44.
and we identified the next code need to port back to nimbus

nimbus-eth1/tests/test_blockchain_json.nim

Line 262 in 2539bd9

if not validateBlockUnchanged(result, preminedBlock):

validateBlockUnchanged will at least fix 4 more test cases.

[jangko]

#726 further reduce failing test cases down to 10 (Berlin, without London)

[jangko]

thanks to @mjfh hard work, we can close this issue now. fixed by #727