new internal items to determine busy processes

where possible, daemons should have internal items to help with assessment of their load and configuration tuning.
common requests include way to figure out how many pollers, trappers etc should be used.

so an item like zabbix[trapper,busy] could help with figuring out whether the current configuration is excessive or lacking.

one problem might be wildly fluctuating values, so grabbing this data every minute or so might not be sufficient.