Add 'cancel spawn' functionality

### Proposed change
I would like to give our HPC cluster users the ability to cancel the spawning process. If they have selected the wrong resources, they may find themselves in the spawning state without the possibility to cancel it and to spawn another job with differently chosen resources.

### Alternative options
The only means to cancel a pending job is ssh'ing into the cluster and do an `scancel ` (SLURM)

### Who would use this feature?
All our HPC users.

### (Optional): Suggest a solution
A button with "cancel spawn" functionality. It simply does a `scancel ` (SLURM) or comparable commands for Torque etc.