Be compatible with and handle new features from Poetry v1.1
### [v1.1.0](https://python-poetry.org/blog/announcing-poetry-1-1-0.html)
- [x] Define minimal Poetry version and update Poetry backend definition
- [x] Update `poetry.lock` changed format, and is no longer compatible with Poetry v1.0
## Later
- [ ] Use `poetry publish --dry-run` in the release jobs instead of PyPI test?
issue