feature: Measure CPU load
It could be useful to determine whether is router is doing well (low load), is under significant load or even overloaded.
Few uses cases:
- There are a lot of services running and some of them are failing or crashing.
- Some services are running slow or unresponsive due to system load.
It should be measured as the beginning of diagnostics run to take a look on overall performance of router at the moment and to avoid being influenced by running diagnostics.