Migrate to Poetry v2 (clients/python/silkaj#499)

now supported by Silkaj and DuniterPy:

• Update pyproject.toml with Poetry v2.0 (#499) (clients/python/silkaj!275 - merged)
• Migrate to Poetry v2 (#215) (clients/python/duniterpy!202 - merged)

Update CI syntax to latest standard and conventions