Optimize `latestRelease` field in `RepositoryNode`

**Is your feature request related to a problem? Please describe.**
When querying the latestRelease field, we get N+1 queries.

**Describe the solution you'd like**
We don't have any optimization hints passed to the `strawnerry_django.field` decorator, but we may just populate this field in the database.

**Are you going to work on implementing this?**

- [ ] Yes
- [x] No

**Additional context**
https://strawberry.rocks/docs/django/guide/optimizer#optimization-hints