Ensure Engine API status/error return values match spec

[geoknee]

Here we are returning a nil error with an invalid status. Above in NewPayloadV4 on L664, the upstream code returns a non-nil error and an invalid status. We should file an issue to audit our overall approach to this, keeping in mind how the CL client (e.g. op-node) will consume these values.

We should let the engine API spec guide us here as much as possible https://ethereum.github.io/execution-apis/api-documentation/

Originally posted by @geoknee in #592 (comment)