Log ttd (#3339)

## Issue Addressed

Resolves #3249 

## Proposed Changes

Log merge related parameters and EE status in the beacon notifier before the merge.


Co-authored-by: Paul Hauner <paul@paulhauner.com>

beacon_node/execution_layer/src/lib.rs

@@ -234,6 +234,16 @@ impl<T: EthSpec> ExecutionLayer<T> {
         &self.inner.executor
     }
 
+    /// Get the current difficulty of the PoW chain.
+    pub async fn get_current_difficulty(&self) -> Result<Uint256, ApiError> {
+        let block = self
+            .engine()
+            .api
+            .get_block_by_number(BlockByNumberQuery::Tag(LATEST_TAG))
+            .await?
+            .ok_or(ApiError::ExecutionHeadBlockNotFound)?;
+        Ok(block.total_difficulty)
+    }
     /// Note: this function returns a mutex guard, be careful to avoid deadlocks.
     async fn execution_blocks(
         &self,
@@ -355,6 +365,29 @@ impl<T: EthSpec> ExecutionLayer<T> {
         self.engine().is_synced().await
     }
 
+    /// Execution nodes return a "SYNCED" response when they do not have any peers.
+    ///
+    /// This function is a wrapper over `Self::is_synced` that makes an additional
+    /// check for the execution layer sync status. Checks if the latest block has
+    /// a `block_number != 0`.
+    /// Returns the `Self::is_synced` response if unable to get latest block.
+    pub async fn is_synced_for_notifier(&self) -> bool {
+        let synced = self.is_synced().await;
+        if synced {
+            if let Ok(Some(block)) = self
+                .engine()
+                .api
+                .get_block_by_number(BlockByNumberQuery::Tag(LATEST_TAG))
+                .await
+            {
+                if block.block_number == 0 {
+                    return false;
+                }
+            }
+        }
+        synced
+    }
+
     /// Updates the proposer preparation data provided by validators
     pub async fn update_proposer_preparation(
         &self,

beacon_node/execution_layer/src/test_utils/handle_rpc.rs

@@ -132,6 +132,15 @@ pub async fn handle_rpc<T: EthSpec>(
 
             Ok(serde_json::to_value(response).unwrap())
         }
+        ENGINE_EXCHANGE_TRANSITION_CONFIGURATION_V1 => {
+            let block_generator = ctx.execution_block_generator.read();
+            let transition_config: TransitionConfigurationV1 = TransitionConfigurationV1 {
+                terminal_total_difficulty: block_generator.terminal_total_difficulty,
+                terminal_block_hash: block_generator.terminal_block_hash,
+                terminal_block_number: block_generator.terminal_block_number,
+            };
+            Ok(serde_json::to_value(transition_config).unwrap())
+        }
         other => Err(format!(
             "The method {} does not exist/is not available",
             other