ST-1303: Fix python 3.10 deprecation and package incompatibilities

Python 10 introduced a number of deprecations and existing python package didn't work properly unless updated. Since the test stage in the pipeline didn't set a specific version for the image to use and that image now uses python 3.10 (unlike python 3.8 when the pipeline was last updated successfully), the test stage was failing.

Updating the python packages to the latest versions did break the molecule test, though, so that wasn't an option in the time available to fix the issue.

The docker image used for testing was then put at docker:19, using alpine Linux 3.13 which uses python 3.8. I've also set the image to python3.8 for the linting stage and the default image to docker:19 for the all pipeline.