Enable/Disable threads on specific programs

[Lusitaniae]

Since threads adds a lot of overhead and cardinality to metrics, would be interesting if we could restrict threads to one of the multiple process monitored by process exporter

[Lusitaniae]

For now doing that on prometheus / scraping side by using metrics relabel

so as to only keep thread metrics for my app1/app2, nothing else

    metric_relabel_configs:
      - action: keep
        source_labels: [__name__, groupname]
        regex: namedprocess_namegroup_thread_.*;(app1|app2).*