Make it more clear which system configurations are officially supported

Overview

Our docs are not clear enough on what operating systems, version etc are supported.

Proposal

1. Update https://gitlab.com/gitlab-org/gitlab-development-kit#system-requirements to be a table of officially support configurations, renaming the section to be 'Support configurations' and strengthening the wording as necessary.
2. Update any other doc to refer to the 'Support configurations' table where necessary so we only have a single source of truth.