Migrate to `uv` package manager

Currently, we are using plain `setuptools` to manage the project and `pipenv` for main/dev dependencies and virtual environments.

What about adopting the [`uv` Python package manager](https://github.com/astral-sh/uv)? Seems to be a valid alternative to other project manager tools like `poetry`. It is getting more and more traction in the Python community, and it would give a fresh new look to the `pddl` package :)