Project-level cluster: allow management project in descendant groups

Background

Extending from !18429 (comment 233296682)

• Project-level cluster is only accessible by the project it is attached to.
• With !18429 (merged), a management project can now also access this project cluster. On the restriction that the management project must be in the same namespace / group as the project.

Problem

We can select subgroup projects as the cluster management project, they will not be chosen for the deployment job (❌). Only the items marked with ✔ will work.

Proposal

Extend deployment job cluster logic to allow management projects which are in descendant groups of the project.

PS, should we remove subgroup projects from that dropdown before we fix this in the backend ?

This page may contain information related to upcoming products, features and functionality. It is important to note that the information presented is for informational purposes only, so please do not rely on the information for purchasing or planning purposes. Just like with all projects, the items mentioned on the page are subject to change or delay, and the development, release, and timing of any products, features, or functionality remain at the sole discretion of GitLab Inc.