Kintsugi on_merge_block tests (#2811)

* Start v1.1.5 updates

* Implement new payload creation logic

* Tidy, add comments

* Remove unused error enums

* Add validate payload for gossip

* Refactor validate_merge_block

* Split payload verification in per block processing

* Add execute_payload

* Tidy

* Tidy

* Start working on new fork choice tests

* Fix failing merge block test

* Skip block_lookup_failed test

* Fix failing terminal block test

* Fixes from self-review

* Address review comments

consensus/state_processing/src/per_block_processing.rs

@@ -295,9 +295,18 @@ pub fn get_new_eth1_data<T: EthSpec>(
     }
 }
 
-/// https://github.com/ethereum/consensus-specs/blob/dev/specs/merge/beacon-chain.md#process_execution_payload
-pub fn process_execution_payload<T: EthSpec>(
-    state: &mut BeaconState<T>,
+/// Performs *partial* verification of the `payload`.
+///
+/// The verification is partial, since the execution payload is not verified against an execution
+/// engine. That is expected to be performed by an upstream function.
+///
+/// ## Specification
+///
+/// Contains a partial set of checks from the `process_execution_payload` function:
+///
+/// https://github.com/ethereum/consensus-specs/blob/v1.1.5/specs/merge/beacon-chain.md#process_execution_payload
+pub fn partially_verify_execution_payload<T: EthSpec>(
+    state: &BeaconState<T>,
     payload: &ExecutionPayload<T>,
     spec: &ChainSpec,
 ) -> Result<(), BlockProcessingError> {
@@ -327,6 +336,23 @@ pub fn process_execution_payload<T: EthSpec>(
         }
     );
 
+    Ok(())
+}
+
+/// Calls `partially_verify_execution_payload` and then updates the payload header in the `state`.
+///
+/// ## Specification
+///
+/// Partially equivalent to the `process_execution_payload` function:
+///
+/// https://github.com/ethereum/consensus-specs/blob/v1.1.5/specs/merge/beacon-chain.md#process_execution_payload
+pub fn process_execution_payload<T: EthSpec>(
+    state: &mut BeaconState<T>,
+    payload: &ExecutionPayload<T>,
+    spec: &ChainSpec,
+) -> Result<(), BlockProcessingError> {
+    partially_verify_execution_payload(state, payload, spec)?;
+
     *state.latest_execution_payload_header_mut()? = ExecutionPayloadHeader {
         parent_hash: payload.parent_hash,
         coinbase: payload.coinbase,