Gloas serve envelope rpc (#8896)

Serves envelope by range and by root requests. Added PayloadEnvelopeStreamer so that we dont need to alter upstream code when we introduce blinded payload envelopes.


  


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

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

Co-Authored-By: dapplion <35266934+dapplion@users.noreply.github.com>

beacon_node/beacon_chain/src/canonical_head.rs

@@ -371,6 +371,13 @@ impl<T: BeaconChainTypes> CanonicalHead<T> {
         Ok((head, execution_status))
     }
 
+    // TODO(gloas) just a stub for now, implement this once we have fork choice.
+    /// Returns true if the payload for this block is canonical according to fork choice
+    /// Returns an error if the block root doesn't exist in fork choice.
+    pub fn block_has_canonical_payload(&self, _root: &Hash256) -> Result<bool, Error> {
+        Ok(true)
+    }
+
     /// Returns a clone of `self.cached_head`.
     ///
     /// Takes a read-lock on `self.cached_head` for a short time (just long enough to clone it).