7311: Wrap peer task system usage in ethScheduler call to match other usages

Signed-off-by: Matilda Clerke <matilda.clerke@consensys.net>

ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/checkpointsync/CheckpointDownloadBlockStep.java

@@ -84,7 +84,7 @@ public class CheckpointDownloadBlockStep {
       final PeerTaskResult<Block> peerTaskResult) {
     final Block block = peerTaskResult.getResult();
     if (synchronizerConfiguration.isPeerTaskSystemEnabled()) {
-      CompletableFuture<Optional<BlockWithReceipts>> futureReceipts = new CompletableFuture<>();
+      return ethContext.getScheduler().scheduleServiceTask(() -> {
         GetReceiptsFromPeerTask task =
                 new GetReceiptsFromPeerTask(
                         List.of(block.getHeader()), new BodyValidator(), currentProtocolSpecSupplier);
@@ -104,11 +104,11 @@ public class CheckpointDownloadBlockStep {
                     "PeerTask response code was success, but incorrect number of receipts returned");
           }
           BlockWithReceipts blockWithReceipts = new BlockWithReceipts(block, transactionReceipts);
-        futureReceipts.complete(Optional.of(blockWithReceipts));
+          return CompletableFuture.completedFuture(Optional.of(blockWithReceipts));
         } else {
-        futureReceipts.complete(Optional.empty());
+          return CompletableFuture.completedFuture(Optional.empty());
         }
-      return futureReceipts;
+      });
 
     } else {
       final org.hyperledger.besu.ethereum.eth.manager.task.GetReceiptsFromPeerTask