Mark canceled prebuilds as canceled instead of failed

[gtsiolis]

Problem to solve

Follow up from #5865 (comment):

@gtsiolis: This is most probably out of the scope of these changes but when canceling a prebuild from the project configurator, the prebuild status on the left side of the configurator falls back to READY. Could we introduce a CANCELED status and use this as a status here? Pasting below an early draft featuring the CANCELED status.

Cross-posting from #5865 (comment):

@jankeromnes Yes, if the prebuild.state actually becomes aborted (what we want to achieve in this PR), then we could display aborted as CANCELED.

[jankeromnes]

/schedule

[jankeromnes]

/assign