[Terraform] Provision GCS Buckets for State and Diff Blobs

[jcscottiii]

Add Terraform configuration (google_storage_bucket resources) to create two new, private GCS buckets: one for storing the 'State Snapshot' blobs (webstatus-state) and one for the 'Mega-Diff' event blobs (webstatus-diffs). The configuration must also include the necessary IAM bindings to grant the EventProducerWorker service account write permissions and the Backend API service account read permissions.