This patch updates the version of the github actions we use in our CI
workflows.
While they still run correctly, they're showing some warnings about
being too out of date in the UI.
Nearly all the github actions we rely on have increased their major
version, at least to update the Node.js version they run on, since the
previous one is being deprecated and will eventually become unsupported.
So this patch updates all the versions of the github actions we use.
Alberto Bertogli