Allow to use cross project pipelines

What does this MR do?

This builds on top of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11685 and extends Pipeline Triggers with the ability to use CI_JOB_TOKEN to trigger dependent pipeline (on the same or another project) and create cross-project relation.

This is DRY code, still to be worked on.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/30716