Add function to update real time estimation

[PatrickKa]

Description

Every time we receive an RF command, the real time estimation is updated. This means computing a new real time offset and storing it in the persistent state. Unfortunately, the real time thread also wants to have write access to the time offset (see #222). A topic (like the time offset) can, however, only have a single publisher. Maybe there is some other Rodos construct that is better suited for this.