Emit CloudEvents for all long running operations on allocations and Function Executors

The events: * Function container creation start * Function container creation success/failure * Function container image pull start * Function container image pull success/failure * Allocation preparation started * Allocation preparation success/failure * Allocation enqued on FE * Allocation started on FE (the list needs to be clarified and checked for completeness) This is needed to avoid "spinners without any updates" in UI. Everything that runs for longer than 3 secs need an event like that.