Use Poetry rather than Conda

[adriencrtr]

Currently we are using conda as environment manager.

Why moving to Poetry ?

Because some of our contributors are facing some troubles with conda when cloning the project.

=== TO DO === :

• [ ] Remove the setup.py and use ".toml" file.
• [ ] Include the environment.dev.yml in the ".toml" file.
• [ ] Include the environment.doc.yml in the ".toml" file.
• [ ] Deal with the environment.ci.yml ?
• [ ] Update the documentation for new contributors.
• [ ] Change Github workflows.