jobs: Put groovy code to update GitLab commit status in an include file

This code snippet is used in numerous Jenkins pipelines so better deduplicating it.

cc @teams/sysadmin (<- @anlambert, @vlorentz just so you know, this then appears in the todo in the upper right corner to the highlighted group/person)

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Migrated from D9003 (view on Phabricator)