Sanitize component model

[jnummelin]

From @twz123 in #4213 (comment)

I still think we should eventually sanitize our component model. Either use the context from Start and don't have a Stop method, or only use the Stop method to stop the component, disregarding the context from Start. There's just no sense in having a Stop method if it's a no-op even for components that are actually running and need to be stopped.

We would need to break up the component interface a bit and go through all the components to use the root context properly.

[twz123]

/xref #1844