Possibility to disable per cpu core stats in metricbeat docker module

[henrikno]

Describe the enhancement:
The docker cpu metrics are extremely detailed when having many cores:

This takes up a lot of storage that we don't need, so we have to filter it out. It would be nice if it was possible to disable it in metricbeat directly.

Suggestion
Config option for enabling/disabling per cpu-core cpu usage.

The same goes for system per process with cgroup stats, which is stored per core. I can open a separate issue for that if necessary.
https://www.elastic.co/guide/en/beats/metricbeat/master/metricbeat-metricset-system-process.html

[jsoriano]

Fixed by #9194

[jsoriano]

I have created #9326 for the cgroup metrics.