ci: uses gitlab-ci 'rules:'

With @nchauvat and other we have observed that only:/except: rules were only applied on the latest commit and not the whole MR which were posing problems for us.

After discussion with the people of heptapod it appears that only:/except: rules are deprecated and that we should move to the new rules: stuff https://docs.gitlab.com/ee/ci/yaml/#rules which is both more powerful and less practical to use and learn.

This MR is an attempt to port all the .gitlab-ci.yml of CW to rules: to see if it fixes the issue.

Once merged I'm going to rebase a bunch of other MRs to see if they are triggered correctly.

I'm doing this before working on integrating yamllint to cube-doctor because I need to write a rules or an only in it.