CI: Add precheck to merge_request builds
- Add preliminary check before running the full build
- MR must not be in draft/wip mode
- Headers must be valid
- Rebase must be done
[A venir] Mise en place de quotas sur nos instances GitLab. Plus d'information sur : https://doc-si.inria.fr/pages/viewpage.action?pageId=129728565
[Coming soon] Quotas installation on our GitLab instances. More information: https://doc-si.inria.fr/pages/viewpage.action?pageId=129728565