Scheduler in standard mode should be able to handle pods with no applicationID defined

The scheduler in plugin mode can handle the case where a Pod is defined with schedulerName: yunikorn but no applicationID set can still be scheduled; it is treated as a non-YuniKorn pod and passed through the default scheduler logic.

However, in the standard deployment mode we don't have any way to handle such pods, as there is no default scheduler embedded. Currently, these pods remain in Pending state but simply vanish from YuniKorn's perspective and are never scheduled, leading to subtle problems and difficult-to-diagnose issues.

It would be useful if these pods could be scheduled anyway, ideally using the same algorithm for applicationID generation that the admission controller uses. This would make standalone yunikorn more useful as a default scheduler replacement.