Heroku Postgres plans offer resource tuning (adjustable CPU, Memory, disk, etc.)

### 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 Postgres

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

As the datasets our customers manage on Heroku Postgres grow, one concern is the disproportionate sizing when scaling to larger plans. In some cases, said datasets may grow substantially, but the computational needs may not, and thus paying for orders of magnitude more resources than necessary (ex: copious amounts of unused RAM and compute when only extra disk will do just fine for a particular workload).

This can create a situation where users feel they're paying for resources they don't need or won't use, and start to see the value in the platform diminish as they find alternatives elsewhere that offer more fine-grained resource allocation.