Event Threat Detection, a built-in service of Security Command Center, has released new detectors

## Feature [Event Threat Detection](https://cloud.google.com/security-command-center/docs/concepts-event-threat-detection-overview), a built-in service of Security Command Center, has released new detectors. The following detectors, which are available in Preview with the Enterprise and Premium tiers of Security Command Center, allow users to manage threats to their Google Cloud Backup and Disaster Recovery assets in Security Command Center: * `BACKUP_DELETE_VAULT` * `BACKUP_DELETE_VAULT_BACKUP` * `BACKUP_DELETE_BACKUP_PLAN_ASSOCIATION` In addition, we updated the existing `BACKUP_REMOVE_PLAN` detector to support findings on Google Cloud Backup and Disaster Recovery assets that are managed in the Google Cloud console. This detector will dynamically generate finding descriptions based on the finding source.