Use project access tokens for the multi-pipeline triggers

What does this MR do?

This allows the scripts/trigger-build script to use new environment variables that contain dedicated Project access token instead of the default $GITLAB_BOT_MULTI_PROJECT_PIPELINE_POLLING_TOKEN variable which is a @gitlab-bot's personal access token that is abused a lot.

A similar change is made in the gitlab-org/omnibus-gitlab project at omnibus-gitlab!5487 (merged), and in the gitlab-org/gitlab-qa project at gitlab-qa!730 (merged)..

The following new project access tokens have been created:

• "Multi-pipeline (from 'gitlab-org/gitlab' 'package-and-qa' job)" at https://gitlab.com/gitlab-org/build/omnibus-gitlab-mirror/-/settings/access_tokens
  • Set as masked variable OMNIBUS_GITLAB_PROJECT_ACCESS_TOKEN at https://gitlab.com/gitlab-org/gitlab/-/settings/ci_cd
• "Multi-pipeline (from 'gitlab-org/gitlab' 'cloud-native-image' job)" at https://gitlab.com/gitlab-org/build/CNG/-/settings/access_tokens
  • Set as masked variable CNG_PROJECT_ACCESS_TOKEN at https://gitlab.com/gitlab-org/gitlab/-/settings/ci_cd
• "Multi-pipeline (from 'gitlab-org/gitlab' 'review-build-cng' job)" at https://gitlab.com/gitlab-org/build/CNG-mirror/-/settings/access_tokens
  • Set as masked variable CNG_MIRROR_PROJECT_ACCESS_TOKEN at https://gitlab.com/gitlab-org/gitlab/-/settings/ci_cd
• "DOCS_PROJECT_API_TOKEN" at https://gitlab.com/gitlab-org/gitlab-docs/-/settings/access_tokens (it was already existing prior to this MR)

Related issues

• https://gitlab.com/gitlab-org/quality/team-tasks/-/issues/943.

Check-list

Pre-merge

• review-build-cng still triggers a downstream pipeline: https://gitlab.com/gitlab-org/gitlab/-/jobs/1441867847
• package-and-qa still triggers a downstream pipeline: https://gitlab.com/gitlab-org/gitlab/-/jobs/1441867850
  • Comment is successfully posted by the new OMNIBUS_GITLAB_PROJECT_ACCESS_TOKEN from https://gitlab.com/gitlab-org/gitlab
  • Comment is successfully posted by the new GITLAB_QA_PROJECT_ACCESS_TOKEN from https://gitlab.com/gitlab-org/gitlab-qa-mirror

Post-merge

• Consider communicating these changes to the broader team following the communication guideline for pipeline changes