Resolve "Enable Cloud Run on GKE cluster creation"

What does this MR do?

Allows users to create Kubernetes clusters on GCP using Cloud Run on GKE to pre-install Knative.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team

Screenshots

Closes #27502 (closed)

This MR was originally reviewed as https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/31790 and moved here per https://gitlab.com/gitlab-org/gitlab-ee/issues/13304

app/models/clusters/concerns/application_status.rb

@@ -27,6 +27,12 @@ module ApplicationStatus
           state :update_errored, value: 6
           state :uninstalling, value: 7
           state :uninstall_errored, value: 8
+
+          # Used for applications that are pre-installed by the cluster,
+          # e.g. Knative in GCP Cloud Run enabled clusters
+          # Because we cannot upgrade or uninstall Knative in these clusters,
+          # we define only one simple state transition to enter the `pre_installed` state,
+          # and no exit transitions.
           state :pre_installed, value: 9
 
           event :make_scheduled do