Enhance DiskFS initialization and error handling

- Updated `disk.New` to support asynchronous initialization for large caches, improving responsiveness during startup.
- Introduced an eviction function parameter to `disk.New`, ensuring proper handling of over-capacity scenarios.
- Enhanced error handling in various components, including memory and disk tests, to ensure robustness and clarity.
- Refactored tests to validate new behaviors, including checks for delayed attachment and proper error propagation.
- Removed obsolete error handling code and tests related to the now-deleted errors package, streamlining the codebase.

cmd/root.go

@@ -141,7 +141,11 @@ var rootCmd = &cobra.Command{
 		logger.Logger.Info().
 			Msg("steamcache2 " + version.Version + " started on " + cfg.ListenAddress)
 
-		sc.Run()
+		if err := sc.Run(); err != nil {
+			logger.Logger.Error().Err(err).Msg("steamcache2 Run failed")
+			fmt.Fprintf(os.Stderr, "Error: steamcache2 run error: %v\n", err)
+			os.Exit(1)
+		}
 
 		logger.Logger.Info().Msg("steamcache2 stopped")
 		os.Exit(0)