ci: Reduce duplication for CNG jobs

Rémy Coutablerequested to merge
393482-reduce-duplication-between-gitlab-ci-release-environments-main-gitlab-ci-yml-and-gitlab-ci into master

What does this MR do and why?

This introduces .gitlab/ci/cng/main.gitlab-ci.yml to reduce duplication between jobs that trigger CNG downstream pipelines.

MR acceptance checklist

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

Related to #393482 (closed)

Edited by Rémy Coutable

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