cache: Short TTL negative cache for 404/410 depot objects

Stop re-fetching gone depot objects on every miss: store 404/410 in the
existing VFS cache under the same key with a short TTL (default 5m).

cmd/root.go

@@ -129,6 +129,7 @@ var rootCmd = &cobra.Command{
 			finalMaxRequestsPerClient,
 			cfg.MaxObjectSize,
 			cfg.TrustedProxies,
+			cfg.Cache.NegativeTTL,
 		)
 		if err != nil {
 			logger.Logger.Error().