ci: 🎡 use cache with poetry

[severo]

No description provided.

[severo]

We have errors, due to the relative dependencies:

 Creating virtualenv admin in /home/runner/work/datasets-server/datasets-server/services/admin/.venv
Installing dependencies from lock file

  RuntimeError

  [BUG]  libutils (0.1.0) is not satisfied.

[severo]

Note that libutils is depended by libcache and libqueue, which are both dependencies of the services. Maybe due to this double dependency (related to this? python-poetry/poetry#1757 (comment) - note that I cannot reproduce: it works for me when launched directly on my machine, the issue seems to be related to the poetry cache in actions/setup-python)

[severo]

Last fix does not work:

Error: Invalid pattern '../../libs/libutils/poetry.lock'. Relative pathing '.' and '..' is not allowed.

[severo]

Last fix: still the same error (https://github.com/huggingface/datasets-server/runs/6622451310?check_suite_focus=true)

 [BUG]  libutils (0.1.0) is not satisfied.

[severo]

The bug is not due to the cache: poetry line!

[severo]

Finally, it works! Seems like we need to:

• install poetry twice (before setup-python, then after, with another method)
• use a global virtualenv, not an in-path env