[Feature] ClusterExecutor - handle cancelled jobs

[jan-janssen]

Handle jobs which are waiting in the queue or jobs which have been cancelled in the queue.

[jan-janssen]

This would also allow us to leverage the standby queue and dynamically rescale the allocation as required. But at the same time, I do not address the regular case of submitting workers to the queue and interacting with those. Maybe this could be another extension.