More robust runner autoscaling

[ZainRizvi]

Goal: Reduce job queuing by increase self hosted runner fleet's autoscaling reliability in the face of failed/dropped scale up requests

The approach

Create a new scheduled lambda function that:

1. Runs every 15 mins
2. Queries ClickHouse for jobs that have been queued for over half an hour
3. Checks the runner types for those jobs to see which ones are self-hosted
4. Invokes the scale up function to scale up the appropriate number of runners of each type to handle the outstanding jobs

[huydhn]

Chatting with @ZainRizvi, this is probably not needed anymore with the ephemeral queuing fixes from the end of last half. We will observe a bit more and close this.