Move multi-project pipelines to Core from Premium

Currently, multi-project pipelines are available on Premium and above only. Based on our buyer-based-pricing-model, this means we consider the feature to be mainly used by Directors and above.

However, I don't think that assumption is not entirely true. Even at GitLab, we have important usecases for this feature at IC level. For example

  1. Building an omnibus-gitlab package from a CE/EE Merge Request - by triggering a pipeline in omnibus-gitlab project as part of CE/EE pipeline.
  2. Review apps for CE/EE depend on our cloud native images being built, which requires triggering a pipeline in CNG project as part of CE/EE pipeline
  3. Running a QA pipeline against a package and docker image - which requires triggering a pipeline in gitlab-qa project from omnibus-gitlab pipeline.

Similarly, any software development scenario where components are in different repos and have dependencies between them could use this feature.

Also, on a slack thread @markpundsack mentioned

As it relates to microservices, multi-project pipelines could be construed as an IC feature. We should consider it when doing the batch re-evaluation of features based on the pricing tiers. IIRC, multi-project pipelines was slotted before that model existed.

I think multi-project feature should be a Core feature, following our buyer-based pricing model.

@jlenny

Edited by Balasankar 'Balu' C