Independent destination states

### Feature description

Currently, the pipeline and all the sources and destinations within it always have the same state, be it running, stopped or something else. That also means that, if a destination malfunctions, the whole pipeline will become degraded, and actually no destination will be running.

This issue is about changing that, so that destinations have independent states, and make it possible that some destinations in a pipeline are running while other destinations in the same pipeline are stopped or degraded.