Log range sync download errors (#6991)

Currently range sync download log errors just say `error: rpc_error` which isn't helpful. The actual error is suppressed unless logged somewhere else.


  Log the actual error that caused the batch download to fail as part of the log that states that the batch download failed.

beacon_node/network/src/sync/range_sync/chain.rs

@@ -2,7 +2,7 @@ use super::batch::{BatchInfo, BatchProcessingResult, BatchState};
 use super::RangeSyncType;
 use crate::metrics;
 use crate::network_beacon_processor::ChainSegmentProcessId;
-use crate::sync::network_context::RangeRequestId;
+use crate::sync::network_context::{RangeRequestId, RpcResponseError};
 use crate::sync::{network_context::SyncNetworkContext, BatchOperationOutcome, BatchProcessResult};
 use beacon_chain::block_verification_types::RpcBlock;
 use beacon_chain::BeaconChainTypes;
@@ -879,6 +879,7 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
         batch_id: BatchId,
         peer_id: &PeerId,
         request_id: Id,
+        err: RpcResponseError,
     ) -> ProcessingResult {
         let batch_state = self.visualize_batch_state();
         if let Some(batch) = self.batches.get_mut(&batch_id) {
@@ -901,9 +902,10 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
             debug!(
                 batch_epoch = %batch_id,
                 batch_state = ?batch.state(),
+                error = ?err,
                 %peer_id,
                 %request_id,
-                "Batch failed. RPC Error"
+                "Batch download error"
             );
             if let Some(active_requests) = self.peers.get_mut(peer_id) {
                 active_requests.remove(&batch_id);