Allow for state root validation on sidechains

[Rjected]

Describe the feature

Many engine API hive tests require that we are able to compute the state root on sidechains, which are produced using newPayload. These tests expect us to return VALID if we can validate the payload in its sidechain, including validating the state root. We currently return ACCEPTED, which other clients only return if they are missing data to validate the sidechain block.

To support this, we would need to:

• unwind state to the point where the sidechain forked off the canonical chain
• apply sidechain state changes
• calculate and validate the merkle root
• re-apply the unwinded changes

Additional context

No response