Design alert signals and thresholds

[polatengin]

As a project developer, I want to predefine the set of telemetry signals and corresponding thresholds that should trigger action, so that project developers can build the necessary supporting queries and IaC

• [ ] Design doc created that outlines the list of telemetry signals that should be used in alerts, with associated thresholds, etc
• [ ] Document references recommended alert rules for all supporting resources (e.g. https://learn.microsoft.com/en-us/azure/azure-monitor/vm/tutorial-monitor-vm-alert-recommended)

[polatengin]

Mentioned in #415