stream: use bitmap in writable state

PR-URL: #49834
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>