* eth: chain config (genesis + fork) ENR entry

* core/forkid, eth: protocol independent fork ID, update to CRC32 spec

* core/forkid, eth: make forkid a struct, next uint64, enr struct, RLP

* core/forkid: change forkhash rlp encoding from int to [4]byte

* eth: fixup eth entry a bit and update it every block

* eth: fix lint

* eth: fix crash in ethclient tests