Do not interpret "latest valid hash" as identifying a valid hash (#3327)

## Issue Addressed

NA

## Proposed Changes

After some discussion in Discord with @mkalinin it was raised that it was not the intention of the engine API to have CLs validate the `latest_valid_hash` (LVH) and all ancestors.

Whilst I believe the engine API is being updated such that the LVH *must* identify a valid hash or be set to some junk value, I'm not confident that we can rely upon the LVH as being valid (at least for now) due to the confusion surrounding it.

Being able to validate blocks via the LVH is a relatively minor optimisation; if the LVH value ends up becoming our head we'll send an fcU and get the VALID status there.

Falsely marking a block as valid has serious consequences and since it's a minor optimisation to use LVH I think that we don't take the risk.

For clarity, we will still *invalidate* the *descendants* of the LVH, we just wont *validate* the *ancestors*.

## Additional Info

NA

beacon_node/beacon_chain/tests/payload_invalidation.rs

@@ -390,7 +390,7 @@ async fn invalid_payload_invalidates_parent() {
     })
     .await;
 
-    assert!(rig.execution_status(roots[0]).is_valid_and_post_bellatrix());
+    assert!(rig.execution_status(roots[0]).is_optimistic());
     assert!(rig.execution_status(roots[1]).is_invalid());
     assert!(rig.execution_status(roots[2]).is_invalid());
 
@@ -532,9 +532,9 @@ async fn pre_finalized_latest_valid_hash() {
 /// Ensure that a `latest_valid_hash` will:
 ///
 /// - Invalidate descendants of `latest_valid_root`.
-/// - Validate `latest_valid_root` and its ancestors.
+/// - Will not validate `latest_valid_root` and its ancestors.
 #[tokio::test]
-async fn latest_valid_hash_will_validate() {
+async fn latest_valid_hash_will_not_validate() {
     const LATEST_VALID_SLOT: u64 = 3;
 
     let mut rig = InvalidPayloadRig::new().enable_attestations();
@@ -571,8 +571,10 @@ async fn latest_valid_hash_will_validate() {
             assert!(execution_status.is_invalid())
         } else if slot == 0 {
             assert!(execution_status.is_irrelevant())
-        } else {
+        } else if slot == 1 {
             assert!(execution_status.is_valid_and_post_bellatrix())
+        } else {
+            assert!(execution_status.is_optimistic())
         }
     }
 }
@@ -693,9 +695,15 @@ async fn invalidates_all_descendants() {
         }
 
         let execution_status = rig.execution_status(root);
-        if slot <= latest_valid_slot {
-            // Blocks prior to the latest valid hash are valid.
+        if slot == 0 {
+            // Genesis block is pre-bellatrix.
+            assert!(execution_status.is_irrelevant());
+        } else if slot == 1 {
+            // First slot was imported as valid.
             assert!(execution_status.is_valid_and_post_bellatrix());
+        } else if slot <= latest_valid_slot {
+            // Blocks prior to and included the latest valid hash are not marked as valid.
+            assert!(execution_status.is_optimistic());
         } else {
             // Blocks after the latest valid hash are invalid.
             assert!(execution_status.is_invalid());
@@ -769,9 +777,15 @@ async fn switches_heads() {
         }
 
         let execution_status = rig.execution_status(root);
-        if slot <= latest_valid_slot {
-            // Blocks prior to the latest valid hash are valid.
+        if slot == 0 {
+            // Genesis block is pre-bellatrix.
+            assert!(execution_status.is_irrelevant());
+        } else if slot == 1 {
+            // First slot was imported as valid.
             assert!(execution_status.is_valid_and_post_bellatrix());
+        } else if slot <= latest_valid_slot {
+            // Blocks prior to and included the latest valid hash are not marked as valid.
+            assert!(execution_status.is_optimistic());
         } else {
             // Blocks after the latest valid hash are invalid.
             assert!(execution_status.is_invalid());

consensus/proto_array/src/proto_array.rs

@@ -491,9 +491,6 @@ impl ProtoArray {
                             node.best_descendant = None
                         }
 
-                        // It might be new knowledge that this block is valid, ensure that it and all
-                        // ancestors are marked as valid.
-                        self.propagate_execution_payload_validation_by_index(index)?;
                         break;
                     }
                 }