Initial Python v3.12 support
Once [first beta is released](https://peps.python.org/pep-0693/) (22nd May 2023), we can introduce Python v3.12 support, to see how it goes:
- [x] docker/python3/poetry#8+
- [x] With `gcc` and `libffi-dev`
- [x] Set up v3.12 test job
- [x] Allow the job to fail with `allow_failure: true`. It shouldn’t block the pipeline
- [x] [We currently have an issue](https://github.com/crate-py/rpds/issues/13) with [`rpds-py`](https://pypi.org/project/rpds-py/) which does not provide Py3.12 wheel. Package introduced with [`jsonschema` v4.18.0](https://github.com/python-jsonschema/jsonschema/blob/main/CHANGELOG.rst#v4180)
```
├── jsonschema ^4.17.3
│ ├── attrs >=22.2.0
│ ├── importlib-resources >=1.4.0
│ │ └── zipp >=3.1.0
│ ├── jsonschema-specifications >=2023.03.6
│ │ ├── importlib-resources >=1.4.0 (circular dependency aborted here)
│ │ └── referencing >=0.28.0
│ │ ├── attrs >=22.2.0 (circular dependency aborted here)
│ │ └── rpds-py >=0.7.0
│ ├── pkgutil-resolve-name >=1.3.10
│ ├── referencing >=0.28.4 (circular dependency aborted here)
│ └── rpds-py >=0.7.1 (circular dependency aborted here)
```
issue