Emit host event for maintenance prepare failure state

[Copilot]

When a host transitions into ErrorInPrepareForMaintenance, CloudStack did not emit a corresponding event, leaving operators without an event signal for this maintenance-preparation failure path. This change adds a dedicated error event and emits it at the state transition.

• Add maintenance prepare error event

  • Introduce EventTypes.EVENT_MAINTENANCE_PREPARE_ERROR = "MAINT.PREPARE.ERROR"
  • Register the event with Host.class in EventTypes.entityEventDetails

• Emit event on failure transition

  • Update ResourceManagerImpl.setHostIntoErrorInPrepareForMaintenance(...) to publish a completed action event after the resource state transition
  • Use EventVO.LEVEL_ERROR so the event is distinguishable from the successful maintenance-prepare flow

• Cover the new behavior

  • Extend ResourceManagerImplTest to verify the error event is emitted
  • Add an assertion for the event-to-entity mapping

ActionEventUtils.onCompletedActionEvent(
        CallContext.current().getCallingUserId(),
        CallContext.current().getCallingAccountId(),
        EventVO.LEVEL_ERROR,
        EventTypes.EVENT_MAINTENANCE_PREPARE_ERROR,
        String.format("failed to prepare host %s for maintenance due to migration or VM state errors", host),
        host.getId(), null, 0);