Migrate existing data from KubernetesService to Clusters::Platforms::Kubernetes

What does this MR do?

V2

SELECT services.*
FROM services
INNER JOIN projects ON projects.id = services.project_id
WHERE services.category = 'deployment' AND services.type = 'KubernetesService' AND
    NOT EXISTS (
        SELECT 1 FROM cluster_platforms_kubernetes
        INNER JOIN cluster_projects ON cluster_projects.project_id = projects.id
        WHERE cluster_projects.cluster_id = cluster_platforms_kubernetes.cluster_id AND
            services.properties LIKE CONCAT('%', cluster_platforms_kubernetes.api_url, '%')
    );

Find target kubernetes_services

SELECT s.active, s.properties, projects.name, clusters.name, cluster_platforms_kubernetes.api_url
FROM services AS s
INNER JOIN projects ON projects.id = s.project_id
INNER JOIN cluster_projects ON projects.id = cluster_projects.project_id
INNER JOIN clusters ON cluster_projects.cluster_id = clusters.id
INNER JOIN cluster_platforms_kubernetes ON cluster_platforms_kubernetes.cluster_id = clusters.id
WHERE s.category = 'deployment' AND s.type = 'KubernetesService' 
    AND (
        cluster_projects.project_id IS NULL -- Cluster doesn't exist
        OR
        s.properties NOT LIKE CONCAT('%', cluster_platforms_kubernetes.api_url, '%')  -- Cluster exists but KubernetesService configured independently
    )
;

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Review
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #40418 (closed)