refactor: switch main package manager to Poetry.

[shahinism]

Pull Request Description

Summary:
This PR sets poetry as the default package manager for Python projects, providing seamless integration with devenv. pdm is not designed to run inside a virtual environment, which leads to various issues. To maintain backward compatibility, users can still opt to switch back to pdm if needed.

Details:

• poetry is now the default package manager for Python due to its compatibility with devenv.
• pdm is known to cause issues within virtual environments, so the initial approach to running it inside venv, is not optimal.
• The option to use pdm remains available for those who prefer it.
• Future support for pdm will be considered once devenv adds support (tracking issue: Support pdm cachix/devenv#703).

Why this change is necessary:

• poetry works smoothly within devenv, whereas pdm introduces complications.
• Ensuring a stable development environment while retaining flexibility for users who prefer pdm.
• In the current version some functionalities of pdm don't work properly like pdm run ... or pdm remove ...

Next steps:

• Once devenv adds support for pdm, we can re-evaluate its usage as the default package manager.

Tracking Issue:

• cachix/devenv#703 for monitoring pdm support in devenv.