ci: Introduce 'gitlab-jh-pipeline' manual job to trigger a JH pipeline

Rémy Coutablerequested to merge
339248-run-a-manually-triggered-jihu-pipeline-within-a-gitlab-org-gitlab-mr into master

What does this MR do?

Enable GitLab team members to run a JiHu pipeline from a gitlab-org/gitlab MR to allow for validation of a change in the JiHu Edition.

Related to #339248 (closed).

Edited by Rémy Coutable

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