gitlab-ci.yml tidying

Per this article: https://medium.com/@imalik8088/tired-of-repeated-gitlab-ci-files-includes-to-the-rescue-17225532812a

There are a number of ways we could potentially beautify/tidy out gitlab-ci.yml file to make it more readable/manageable. Would like to implement these.

Here's an uber example here: https://gitlab.com/gitlab-org/gitlab-foss/-/blob/master/.gitlab-ci.yml