Draft: Resolve "Support merged results for as-if-jh pipeline"

From Draft to Ready

• Testing commit is removed (!118907 (22c69d24))
• The code from gitlab-org-sandbox/gitlab-jh-validation!1 (closed) is in this MR

Context

Related to #386585 (closed)

What does this MR do and why?

• Create an MR in the JH validation project in the prepare-as-if-jh-branch job
• Remove the FORCE_GITLAB_CI flag when triggering the JH validation pipeline (legacy flag)
• [Draft] Add a workflow::rules from gitlab-org-sandbox/gitlab-jh-validation!1 (closed) into this MR

Does it work?

TODO: Add this section

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.