Builder Specs v0.2.0 (#3134)

## Issue Addressed

https://github.com/sigp/lighthouse/issues/3091

Extends https://github.com/sigp/lighthouse/pull/3062, adding pre-bellatrix block support on blinded endpoints and allowing the normal proposal flow (local payload construction) on blinded endpoints. This resulted in better fallback logic because the VC will not have to switch endpoints on failure in the BN <> Builder API, the BN can just fallback immediately and without repeating block processing that it shouldn't need to. We can also keep VC fallback from the VC<>BN API's blinded endpoint to full endpoint.

## Proposed Changes

- Pre-bellatrix blocks on blinded endpoints
- Add a new `PayloadCache` to the execution layer
- Better fallback-from-builder logic

## Todos

- [x] Remove VC transition logic
- [x] Add logic to only enable builder flow after Merge transition finalization
- [x] Tests
- [x] Fix metrics
- [x] Rustdocs


Co-authored-by: Mac L <mjladson@pm.me>
Co-authored-by: realbigsean <sean@sigmaprime.io>

testing/execution_engine_integration/src/test_rig.rs

@@ -3,7 +3,9 @@ use crate::execution_engine::{
 };
 use crate::transactions::transactions;
 use ethers_providers::Middleware;
-use execution_layer::{ExecutionLayer, PayloadAttributes, PayloadStatus};
+use execution_layer::{
+    BuilderParams, ChainHealth, ExecutionLayer, PayloadAttributes, PayloadStatus,
+};
 use fork_choice::ForkchoiceUpdateParameters;
 use reqwest::{header::CONTENT_TYPE, Client};
 use sensitive_url::SensitiveUrl;
@@ -14,7 +16,7 @@ use task_executor::TaskExecutor;
 use tokio::time::sleep;
 use types::{
     Address, ChainSpec, EthSpec, ExecutionBlockHash, ExecutionPayload, FullPayload, Hash256,
-    MainnetEthSpec, Slot, Uint256,
+    MainnetEthSpec, PublicKeyBytes, Slot, Uint256,
 };
 const EXECUTION_ENGINE_START_TIMEOUT: Duration = Duration::from_secs(20);
 
@@ -305,6 +307,11 @@ impl<E: GenericExecutionEngine> TestRig<E> {
         // in CI.
         sleep(Duration::from_secs(3)).await;
 
+        let builder_params = BuilderParams {
+            pubkey: PublicKeyBytes::empty(),
+            slot: Slot::new(0),
+            chain_health: ChainHealth::Healthy,
+        };
         let valid_payload = self
             .ee_a
             .execution_layer
@@ -313,9 +320,9 @@ impl<E: GenericExecutionEngine> TestRig<E> {
                 timestamp,
                 prev_randao,
                 proposer_index,
-                None,
-                Slot::new(0),
                 forkchoice_update_params,
+                builder_params,
+                &self.spec,
             )
             .await
             .unwrap()
@@ -413,6 +420,11 @@ impl<E: GenericExecutionEngine> TestRig<E> {
         let timestamp = valid_payload.timestamp + 1;
         let prev_randao = Hash256::zero();
         let proposer_index = 0;
+        let builder_params = BuilderParams {
+            pubkey: PublicKeyBytes::empty(),
+            slot: Slot::new(0),
+            chain_health: ChainHealth::Healthy,
+        };
         let second_payload = self
             .ee_a
             .execution_layer
@@ -421,9 +433,9 @@ impl<E: GenericExecutionEngine> TestRig<E> {
                 timestamp,
                 prev_randao,
                 proposer_index,
-                None,
-                Slot::new(0),
                 forkchoice_update_params,
+                builder_params,
+                &self.spec,
             )
             .await
             .unwrap()