Cleanup F3 API to use Run/Start and Stop instead of context for lifetime

[Kubuxu]

@Stebalien do you have a preference for Start vs Run (Start would not block, Run would)?

[Stebalien]

We now use Start/Stop so we can wait for initialization to finish. Unfortunately, we have no way to detect if a service exited early.

On the other hand... we may want to change some of our services to not exit early and instead restart themselves?

[Stebalien]

See #422