[Request] Add support for pg_repack extension on Heroku Postgres

### 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?

Postgres

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

```markdown
Title pretty much says it all. Without pg_repack, the only way to reclaim disk space is really `REINDEX INDEX CONCURRENTLY`, `VACUUM FULL`, and `pg:copy`, the latter two of which are pretty invasive and require downtime. `pg_repack` would be a big help! There is also `pg_squeeze

https://github.com/reorg/pg_repack
https://github.com/cybertec-postgresql/pg_squeeze
```