Support multi project pipeline on the same project

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Summary

USers would like to create a new downstream multi-project pipeline on the same project

Steps to reproduce

Consider following .gitlab-ci.yml on project my/project

Test Downstream:
  stage: deploy
  when: manual
  trigger:
    project: my/project

Use case

My use case here is that I have a n projects that must run their flow whenever any of these projects runs. So having project A, B, C when A is triggered then B and C must trigger as well. When B triggers, A and C must trigger as well.

The n number of projects is arbitrary hence there's a logic (in every project) that generates .yml file with jobs that trigger A, B and C (and possibly D, E, ... as well) which is then executed as a child job. (see https://docs.gitlab.com/ee/ci/parent_child_pipelines.html#dynamic-child-pipelines)

Those projects run the same jobs when triggered in through a multi-project pipeline thus I don't want to leave any project out of it.

Edited by 🤖 GitLab Bot 🤖