[Task Manager] Use cgroup data in fallback match of stream PIDs with applications
Task Manager tries to show an audio icon for the application playing audio. This is problematic for the case of multi-process applications, such as a modern browser where multiple PIDs are involved. Various heuristics have been tried, currently we try to see if the parent PIDs match anything, but we seem to just alternate between different bugs.
In new Plasma we have cgroup information which puts processes together when they are launched. This should be a lot more accurate.
This won't work on BSD, but this code is only used in fallback cases anyway for a non-core feature.