Check if load balancing is unbalanced.

[widhalmt]

Check if the checks are evently distributred between nodes within an zone.

When this new feature is implemented, we should collect some sample data from setups and then introduce thresholds for anomaly detection.

Ways to find if the nodes are unbalanced are discribed in https://www.icinga.com/docs/icinga2/latest/doc/15-troubleshooting/#late-check-results-in-distributed-environments and https://www.icinga.com/2016/08/11/analyse-icinga-2-problems-using-the-console-api/