Initial Custom Metrics - Node & Task Heartbeat

[nharper285]

Summary of the Pull Request

What is this about?
In order to improve the reliability of OneFuzz's telemetry - and therefore the Grafana data dashboards that rely on it - we are pursuing a refactor that makes use of App Insight's CustomMetrics type. These metrics are, importantly, not sampled and will offer us a more consistent monitoring type without fear of sampling.

In order to centralize and standardize the CustomMetric format, we are making use of a set of 'metrics' types and functions. Funneling all of the logging through this one source will allow us to keep better track of the creation of the actual metric and, again, standardize the metric's format - name, value, custom dimensions.

To start, I have implemented custom metrics for the node_heartbeat event and the task_heartbeat event.

PR Checklist

• Applies to work item: Replace Desired Traces & Custom Events w/ Custom Metrics to Avoid Sampling #2750
• CLA signed. If not, go over here and sign the CLI.
• Tests added/passed
• Requires documentation to be updated
• I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

Info on Pull Request

What does this include?

• New 'metrics' types
• node and task heartbeat metrics

Validation Steps Performed

How does someone test & validate?