EIP-3675: Upgrade consensus to Proof-of-Stake

[timbeiko]

Discussion item for the Merge EIP, which now has an open PR: ethereum/EIPs#3675

[timbeiko]

Consensus API draft spec: https://hackmd.io/@n0ble/consensus_api_design_space

[timbeiko]

Sync spec: https://github.com/fjl/p2p-drafts/blob/master/merge-sync/merge-sync.md

[timbeiko]

Closing this issue as this is now part of the EL merge spec