insights: add monitoring alerts for insights query queue

Created by: coury-clark

Code insights query queue has no alerts due to instability in the past. We would like to start alerting on some basic metrics on dogfood to get a sense of what makes sense as an alert. The idea is to capture some basic telemetry around the question of "is code insights processing queries". In the future, we will build more telemetry around measuring the performance of this processing.

Something like:

• Queue has records and queue handler rate = 0 for 15 minutes -> warning
• Queue returns null vector for 15 minutes -> warning