Adaptor for fastify@v5

### Feature description

Currently, PostGraphile supports Fastify version 4 only. However, with the recent release of [Fastify version 5](https://github.com/fastify/fastify/releases/tag/v5.0.0), we aim to extend our support to include this latest version

### Supporting development

I [tick all that apply]:

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