Gloas ensure we emit payload attributes SSE event (#9348)

https://github.com/sigp/lighthouse/issues/8817

we were not emitting payload attribute SSE events for gloas. Since the head snapshot stores the canonical latest execution payload envelope we have all the info we need to emit the event.


  


Co-Authored-By: Eitan Seri-Levi <eserilev@ucsc.edu>

Co-Authored-By: Eitan Seri-Levi <eserilev@gmail.com>

common/eth2/src/types.rs

@@ -1154,9 +1154,9 @@ pub struct SseExtendedPayloadAttributesGeneric<T> {
     #[serde(with = "serde_utils::quoted_u64")]
     pub proposer_index: u64,
     pub parent_block_root: Hash256,
-    #[serde(with = "serde_utils::quoted_u64")]
-    pub parent_block_number: u64,
-
+    // TODO(gloas) can remove this field once we fork to gloas
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub parent_block_number: Option<Quoted<u64>>,
     pub parent_block_hash: ExecutionBlockHash,
     pub payload_attributes: T,
 }