EIP-4788 Beacon Block Root accessible from EVM

[ryanschneider]

I feel like we should add a parentBeaconBlockRoot field to the "block" schema:

execution-apis/src/schemas/block.yaml

Line 24 in 9c873c2

properties:

I'm definitely open to another name, but that's the name used in the Engine API: #420

[ralexstokes]

this is separate but we also want to extend this schema for the 4844 changes w/ blob gas