Ability to see egress bandwidth for our app

### 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 apps

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

For apps that make a large amount of external requests (third-party APIs, LLMs, etc), it would be great to be able to see how much bandwidth we are using. We are using an API that has usage-based billing for how many GB/month of "data transfer" we do over their API and it's hard for us to confirm and estimate pricing without access to this number.

Heroku Support was very helpful in sharing what metrics they did have, but there was not any granularly for HTTP vs database network traffic and was limited to web dynos.

I know Heroku has a soft limit for monthly network bandwidth and it would also help us to plan accordingly to know if and when we are getting close to those limits to proactively reach out.