Eth2 Specification changes for the Eth1 & Eth2 "Merge"

Eth2.0 Specification PR: https://github.com/ethereum/eth2.0-specs/pull/2229

Proposal on EthResearch: https://ethresear.ch/t/executable-beacon-chain/8271

Related Tweet by @mkalinin: https://twitter.com/mkalinin2/status/1370029361932476417