Consolidate CI jobs

Summary

With the new version of Gitlab, we now have a rules section that allows us to use conditionals.

We could use this to reduce the amount of duplication in the CI, by merging wsl non-master and master, and the same for windows jobs.

Something like:

  rules:
    - if: '$CI_COMMIT_REF_NAME == $CI_DEFAULT_BRANCH'
    - when: manual

would help.

However, the implementation is currently suboptimal, and needs to be fixed. gitlab-org/gitlab#34756 (closed) to track upstream