blob save fsync feature flag (#13652)

Co-authored-by: Kasey Kirkham <kasey@users.noreply.github.com>

config/features/config.go

@@ -69,7 +69,8 @@ type Flags struct {
 	EnableEIP4881                bool // EnableEIP4881 specifies whether to use the deposit tree from EIP4881
 
 	PrepareAllPayloads bool // PrepareAllPayloads informs the engine to prepare a block on every slot.
-
+	// BlobSaveFsync requires blob saving to block on fsync to ensure blobs are durably persisted before passing DA.
+	BlobSaveFsync bool
 	// KeystoreImportDebounceInterval specifies the time duration the validator waits to reload new keys if they have
 	// changed on disk. This feature is for advanced use cases only.
 	KeystoreImportDebounceInterval time.Duration
@@ -245,6 +246,11 @@ func ConfigureBeaconChain(ctx *cli.Context) error {
 		logEnabled(EnableLightClient)
 		cfg.EnableLightClient = true
 	}
+	if ctx.IsSet(BlobSaveFsync.Name) {
+		logEnabled(BlobSaveFsync)
+		cfg.BlobSaveFsync = true
+	}
+
 	cfg.AggregateIntervals = [3]time.Duration{aggregateFirstInterval.Value, aggregateSecondInterval.Value, aggregateThirdInterval.Value}
 	Init(cfg)
 	return nil