op-program: Use retrying RPC when fetching state nodes and code.

Refactors creation of RPC clients to ensure only the retrying wrapper can be used.

op-program/host/host.go

@@ -192,28 +192,25 @@ func PreimageServer(ctx context.Context, logger log.Logger, cfg *config.Config,
 
 func makePrefetcher(ctx context.Context, logger log.Logger, kv kvstore.KV, cfg *config.Config) (*prefetcher.Prefetcher, error) {
 	logger.Info("Connecting to L1 node", "l1", cfg.L1URL)
-	l1RPC, err := client.NewRPC(ctx, logger, cfg.L1URL)
+	l1RPC, err := createRetryingRPC(ctx, logger, cfg.L1URL)
 	if err != nil {
 		return nil, fmt.Errorf("failed to setup L1 RPC: %w", err)
 	}
 
 	logger.Info("Connecting to L2 node", "l2", cfg.L2URL)
-	l2RPC, err := client.NewRPC(ctx, logger, cfg.L2URL)
+	l2RPC, err := createRetryingRPC(ctx, logger, cfg.L2URL)
 	if err != nil {
 		return nil, fmt.Errorf("failed to setup L2 RPC: %w", err)
 	}
 
-	l1Backoff := opclient.NewRetryingClient(l1RPC, maxRPCRetries)
-	l2Backoff := opclient.NewRetryingClient(l2RPC, maxRPCRetries)
-
 	l1ClCfg := sources.L1ClientDefaultConfig(cfg.Rollup, cfg.L1TrustRPC, cfg.L1RPCKind)
-	l1Cl, err := sources.NewL1Client(l1Backoff, logger, nil, l1ClCfg)
+	l1Cl, err := sources.NewL1Client(l1RPC, logger, nil, l1ClCfg)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create L1 client: %w", err)
 	}
 
 	l2ClCfg := sources.L2ClientDefaultConfig(cfg.Rollup, true)
-	l2Cl, err := sources.NewL2Client(l2Backoff, logger, nil, l2ClCfg)
+	l2Cl, err := sources.NewL2Client(l2RPC, logger, nil, l2ClCfg)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create L2 client: %w", err)
 	}
@@ -222,6 +219,14 @@ func makePrefetcher(ctx context.Context, logger log.Logger, kv kvstore.KV, cfg *
 	return prefetcher.NewPrefetcher(logger, l1Cl, l2DebugCl, kv), nil
 }
 
+func createRetryingRPC(ctx context.Context, logger log.Logger, url string) (client.RPC, error) {
+	rpc, err := client.NewRPC(ctx, logger, url)
+	if err != nil {
+		return nil, err
+	}
+	return opclient.NewRetryingClient(rpc, maxRPCRetries), nil
+}
+
 func routeHints(logger log.Logger, hHostRW io.ReadWriter, hinter preimage.HintHandler) chan error {
 	chErr := make(chan error)
 	hintReader := preimage.NewHintReader(hHostRW)