Eth1+eth2 client relationship

[axic]

@djrtwo

eth2-client with stateless eth1-engine

To run a validator, an eth2-client must be run with an adjunct eth1-engine. This can be done in a stateless manner (not storing entire eth1 state locally) because eth1 shard-blocks have witnesses available for execution.

I wonder if the BLOCKHASH opcode has any effect on this concept (see The curious case of BLOCKHASH and Stateless Ethereum).The wording seems to suggest in this case the eth2 client would solely rely on the block + block witness and nothing else.