chore: remove builder_index from produce_block_v4 (#9267)

Part of #8828 for the stateful path and helps align gloas `produceBlockV4` with beacon-APIs [PR](https://github.com/ethereum/beacon-APIs/pull/580)


  - Plumb `include_payload` query through the handler. Ignored for now since stateless mode isn't wired up yet
- Add `execution_payload_included` metadata field + `Eth-Execution-Payload-Included` header per spec. Both `false` until stateless lands
- Drop the `{builder_index}` segment from the envelope GET URL since no longer included in spec


Co-Authored-By: shane-moore <skm1790@gmail.com>

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

beacon_node/http_api/src/version.rs

@@ -5,7 +5,8 @@ use eth2::beacon_response::{
 };
 use eth2::{
     CONSENSUS_BLOCK_VALUE_HEADER, CONSENSUS_VERSION_HEADER, CONTENT_TYPE_HEADER,
-    EXECUTION_PAYLOAD_BLINDED_HEADER, EXECUTION_PAYLOAD_VALUE_HEADER, SSZ_CONTENT_TYPE_HEADER,
+    EXECUTION_PAYLOAD_BLINDED_HEADER, EXECUTION_PAYLOAD_INCLUDED_HEADER,
+    EXECUTION_PAYLOAD_VALUE_HEADER, SSZ_CONTENT_TYPE_HEADER,
 };
 use serde::Serialize;
 use types::{ForkName, InconsistentFork, Uint256};
@@ -88,6 +89,19 @@ pub fn add_execution_payload_blinded_header<T: Reply>(
     .into_response()
 }
 
+/// Add the `Eth-Execution-Payload-Included` header to a response.
+pub fn add_execution_payload_included_header<T: Reply>(
+    reply: T,
+    execution_payload_included: bool,
+) -> Response {
+    reply::with_header(
+        reply,
+        EXECUTION_PAYLOAD_INCLUDED_HEADER,
+        execution_payload_included.to_string(),
+    )
+    .into_response()
+}
+
 /// Add the `Eth-Execution-Payload-Value` header to a response.
 pub fn add_execution_payload_value_header<T: Reply>(
     reply: T,