Update EIP-7685: remove requests from block body

[lightclient]

This PR removes the requests from the block body. This change is motivated by a simplification to the engine api: ethereum/execution-apis#591

Make EL validate requestsHash as a part of blockHash validation, note there is no need to keep requests_hash in the beacon block. CLs that run blockHash validation on their own will still be able to do that by implementing the algo EL uses to compute requestsHash
Make EL validate requestsHash in the EL block header against requests obtained from transaction execution

[eth-bot]

✅ All reviewers have approved.

[marioevz]

One small comment.

[marioevz]

From Mikhail's comment in #591 description:

Use concatenation to compute the resulting list of all requests instead of RLP, i.e. do executionRequests = requests_00 || requests_01 || requests_02 instead of requests = RLP([requests_00, requests_01, requests_02]). And use the executionRequests in Engine API and in requestsHash computation, the latter can be as simple as requestsHash = executionRequests(requests)

It seems like this should also be updated to:

Suggested change

	return keccak256(rlp.encode([rlp.encode(req) for req in list]))
	return keccak256(b"".join(list))

Or something along the lines.

[lightclient]

superseded by #8924