Log/handle failure when zipping (large) job folder

[tcompa]

Ref https://github.com/fractal-analytics-platform/fractal-server/blob/main/fractal_server/zip_tools.py#L125.

We did observe the creation of a zip file (for a large folder of ~900 MB) which probably failed, since unzipping it leads to

End-of-central-directory signature not found.  Either this file is not
  a zipfile, or it constitutes one disk of a multi-part archive.  In the
  latter case the central directory and zipfile comment will be found on
  the last disk(s) of this archive.

If _create_zip fails, we should at the very least:

• emit an error log
• remove the corrupted archive