cephrgw: remove cnpg backup buckets (ec migration step 2) (#315)

Step 2 of the ec placement migration: with purge-on-delete now allowed (#313), removing the Bucket CRs makes the operator delete the underlying RGW buckets and their objects, freeing the names to be recreated on ec in step 3.

- remove the nine cnpg backup Bucket resources
- keep ObjectStoreUser and ScheduledBackup so the backup-s3 secrets and schedules survive

Reviewed-on: #315
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>

apps/base/artifactapi/cnpg_backup.yaml

@@ -20,25 +20,6 @@ spec:
   # in-flight restore can still reach the archive.
   retainOnDelete: true
 ---
-apiVersion: ceph.unkin.net/v1alpha1
-kind: Bucket
-metadata:
-  name: cnpg-artifactapi
-  namespace: artifactapi
-spec:
-  placementTarget: ec
-  bucketName: cnpg-artifactapi
-  # The owner user has full control of its own bucket (read + write), which is
-  # all the backup/restore identity needs — no extra BucketAccess grant.
-  ownerRef: cnpg-artifactapi-backup
-  versioning: false
-  tags:
-    app: artifactapi
-    purpose: cnpg-backup
-  # Never drop the backups if the CR is removed; retire buckets by hand.
-  retainOnDelete: false
-  purgeOnDelete: true
----
 # Nightly base backup. Continuous WAL archiving is always-on via the Cluster's
 # spec.backup.barmanObjectStore; this schedules the periodic full backup that
 # WAL is layered on top of. Schedules are staggered across clusters so the 8