Handle challenge deletion and/or name changes

I currently use ctfcli like an infrastructure-as-code provider in CI/CD pipelines. However, the following resource changes (challenges/containers/services) must be reconciled manually:
* Name changes, as it's the sync anchor
* Resource deleted from repo

Other providers like [Azure](https://learn.microsoft.com/en-us/azure/azure-resource-manager/templates/deployment-modes) offer a "complete" mode, where resources that aren't defined in the repo are deleted. This would support the change types listed above.

Not sure whether this aligns to ctfcli's design though - maybe a Terraform provider would be a better fit, since it's common for CTF infrastructure anyway.