Support for Eco dynos for Heroku Teams / Allow Dyno idling for more app types

### 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?

Teams

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

I'm a [big fan](https://twitter.com/searls/status/1589999182957486081?s=20&t=_Q7j1nZg-G8XPfyU2AOXdg) of the middle ground Heroku has claimed after sunsetting free dynos & Postgres with Eco subscriptions and the PG Mini plan.

As I've worked through all my personal and work-related apps to ensure we're ready for the end of the free tier, I've decided we've gotten to the point that we should move @testdouble to Heroku Teams. However, the fact that every staging & review app would need to move to full-priced hobby dynos is holding me back from migrating to Heroku Teams.

Because our company is a consultancy, our blog (as opposed to a software product) is probably our most active Heroku app. We have dozens of consultants who contribute blog posts as pull requests for review by non-technical colleagues (for copyediting, to validate how the article looks, etc.), and Review Apps are an absolutely brilliant tool for the job. Sometimes a blog post takes several weeks or months of review and iteration before being published, so it's not uncommon for us to have relatively long-lived branches and review apps that are almost always asleep and consume very few resources.

As a result of all this, it'd really make a huge difference to our overall cost if we could leverage Eco dynos in Teams, _at least_ for review apps and staging apps. I understand why the Free dyno tier was always excluded from Teams and Enterprise, but since Eco is a paid product tied to uptime, I think it's worth revisiting the decision and allowing them for Teams.