Use *Poetry* instead of *setuptools*

[saroad2]

Is your feature request related to a problem? Please describe.
While using setuptools has been the go-to approach when creating packages in python, in the last few years other tools has been available for the same need. One of those tools is Poetry, which has been adopted by a variety of projects.

After comparing setuptools and Poetry, I've decided to use Poetry as Statue's packaging platform.

Describe the solution you'd like
We need to migrate from setuptools to Poetry. This includes the following:

• Replace the setup.py and setup.cfg files with pyproject.toml
• Make sure all dependencies are installed correctly
• Lock versions using poetry lock and publish to repo
• Make sure we can run tests in correctly in Tox
• Add the Statue script to pyproject.toml
• Update Statue version in pyproject.toml using bump2version.
• Make sure we can deploy Statue using poetry publish
• Use Poetry to publish Statue in CI process

Describe alternatives you've considered
One option is that we can keep using setuptools. The problem with that is that we will have to keep editing setup.cfg and setup.py manually since there is no easy command line tool for doing it.

Another option is to use Hatch. While hatch seems promising (and can also replace the usage of Tox), it "only" has 2.7K stars in Github while Poetry has 20.7K for the time of opening this issue. For the time being, I prefer moving forward with Poetry.