postgres.js pool support

### Feature description

I think Worker should ideally be able to accept a pool from either node-postgres or postgres.js

### Motivating example

I am currently working on a project that connects to the db using postgres.js, my app does not use node-postgres anywhere, and ideally I shouldn't be required to add another adapter.

### Breaking changes

I don't believe this should constitute a breaking change

### Supporting development

I [tick all that apply]:

- [ ] am interested in building this feature myself
- [x] am interested in collaborating on building this feature
- [x] am willing to help testing this feature before it's released
- [x] am willing to write a test-driven test suite for this feature (before it exists)
- [x] am a [Graphile sponsor](https://www.graphile.org/sponsor/) ❤️
- [ ] have an active [support or consultancy contract](https://www.graphile.org/support/) with Graphile