Auto-scaling for background processes

### Required Terms

- [X] I agree to follow this project's [Code of Conduct](https://github.com/heroku/roadmap/blob/main/CODE_OF_CONDUCT.md)
- [X] I have read and accept the [Salesforce Program Agreement](https://www.salesforce.com/company/program-agreement/)

### What service(s) is this request for?

Heroku dynos

### Tell us about what you're trying to solve. What challenges are you facing?

We have a lot of background tasks across our applications that have different scaling characteristics. In the past we have used k8s tools like [keda](https://keda.sh/) to support auto-scaling containers up and down based on events and job queues. It would be great if Heroku had a solution for this.