Show installed libraries and their versions in CI jobs
# What does this PR do?

Whenever there is a need to check
  - if the versions of install libraries change
  - and/or find out which ones change

it is not super easy to get this information.

This PR adds `pip freeze | tee installed.txt` to
  - show the results
  - save to a file
  - and upload as an artifact.

It makes the access to this information easier, and potentially make the process to **get the difference** between previous/current runs easier too.

Example run job (and the artifact): [here](https://app.circleci.com/pipelines/github/huggingface/transformers/50778/workflows/cf542f91-cc42-4942-bac8-100436555dda/jobs/606945)

I plan to do the same for GH actions jobs, but maybe in another PR :-)
_The documentation is not available anymore as the PR was closed or merged._