Move Prometheus-Cluster classes from EE to CE

Summary

Contributes to #42640 (closed)

Move classes related to Prometheus clusters from EE domain to CE.

graph TB
  A[AlertsController] --> B[Clusters:Applications::ScheduleUpdateService]

  subgraph " "
    B --> C[ClusterUpdateAppWorker]
    C --> D[Clusters::Applications::PrometheusUpdateService]
    D --> E[ClusterWaitForAppUpdateWorker]
    E --> F[CheckUpgradeProgressService] --> E
    D --> G[Applications::PrometheusConfigService]
    G --> H(Project.environments_for_scope)
  end		

Improvements

Moving Prometheus alerts from EE to CE requires a lot of code changes. All the required changes can be split and moved in several steps (as described here).

Risks

Involved components

• Clusters::Applications::ScheduleUpdateService
• ClusterUpdateAppWorker
• Clusters::Applications::PrometheusUpdateService
• ClusterWaitForAppUpdateWorker
• CheckUpgradeProgressService
• Applications::PrometheusConfigService
• Project.environment_for_scope method

Optional: Intended side effects

Optional: Missing test coverage