refactor(notification): use new queue package (#9360)

# Which Problems Are Solved

The recently introduced notification queue have potential race conditions.

# How the Problems Are Solved

Current code is refactored to use the queue package, which is safe in
regards of concurrency.

# Additional Changes

- the queue is included in startup
- improved code quality of queue

# Additional Context

- closes https://github.com/zitadel/zitadel/issues/9278

internal/command/instance.go

@@ -851,9 +851,6 @@ func (c *Commands) prepareSetDefaultLanguage(a *instance.Aggregate, defaultLangu
 			if err := domain.LanguageIsAllowed(false, restrictionsWM.allowedLanguages, defaultLanguage); err != nil {
 				return nil, err
 			}
-			if err != nil {
-				return nil, err
-			}
 			return []eventstore.Command{instance.NewDefaultLanguageSetEvent(ctx, &a.Aggregate, defaultLanguage)}, nil
 		}, nil
 	}