Provide support for Open Source metrics

[pmarkowsky]

For larger deployments we'd like Santa to be able to export metrics for use with monitoring solutions like prometheus, or osquery.

[pmarkowsky]

For background, at Google we're using Monarch to monitor our agents specifically CPU/memory usage, look for crash loops and other reliability metrics. Having the Santa integrated helps us find issues like crashes / CPU spikes after rule syncs and other oddities. Additionally this lets us track statistics over time such as how much of the fleet is in lockdown mode and stays in lockdown mode or how often are folks updating rules. Internally we're working to make it easy for Santa to work with our monitoring solution like the rest of our agents.

That said I suggested prometheus and other solutions out there to try and make this a feature that isn't just for Google and others can use it if they'd like.