Add gitlab-managed option to clusters form (!26565) · Merge requests · GitLab.org / GitLab FOSS

What does this MR do?

Add "gitlab-managed" option to Clusters form

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Documentation created/updated via this MR
Documentation reviewed by technical writer or follow-up review issue created
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Add a new column to Clusters::Cluster. It could be:
- Boolean managed. In this case, we need to default to true - https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/26675
Rename current Clusters::Cluster#managed? method to user_provided?, so we can use managed? - https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/26567
Add the new field in the view, pass it to the controller and ensure is saved in database. - https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/26096
Ensure this field is not editable on the Cluster form after the cluster has been created
If managed avoid creation of Kubernetes resources for GCP and user clusters.
- When ci_preparing_state is not enabled
- When ci_preparing_state is enabled
Manual QA