feat: support poetry v2

`poetry` v2 just got released: https://github.com/python-poetry/poetry/releases/tag/2.0.0

Let's add support for it and it's new features, if any
- new lock file format?
- any new `pytproject.toml` declarations
- support for PEP621 - metadata and dependencies
Goal: not either/or, but simultaneously the "old" `tool.poetry` and the "new" `project`
> Add support for the `project` section in the `pyproject.toml` file according to PEP 621
-- https://github.com/python-poetry/poetry/pull/9135
-- https://github.com/python-poetry/poetry/pull/9917
- investigate what else is new ... TBC ...
- ... TBC ...
- tests
- since poetry v2 there is a new lock file format in town: `2.1`. this means we can keep current test structures and add a new folder for each lockfile thing where needed.
- some new cases may not be available for older poetry - like the PEP621 in all its variants... -

[⤴ this list will be updated continuously based on comments below, until the initial feature was provided eventually]

Start by reviewing the existing Poetry parsing and test structure, then compare the Poetry v2 release notes and the linked PEP 621 changes. Identify how pyproject.toml metadata and dependencies and the 2.1 lock file are currently handled. Done means Poetry v2 inputs are supported alongside existing tool.poetry cases, with new lock-file folders and tests for applicable PEP 621 variants.

索引モデルが issue の本文から書いたものです。