Persistedstate

- Changing the state object is thread safe now.

- Remove Python 3.7 support
- Add Python 3.12 support

- Fix crash when the PersistedState is subclassed or constructed from another module
- Make vacuum more failure tolerant. In some edge cases it was possible for the state at beginning to overlap the state at the end.
- Internal: use `pyproject.toml` instead of `setup.py`

- Map the whole YAML file, so modification of nested objects are also persisted immediately

- In-file vacuuming

- Use YAML file format, not just a subset of YAML