Add templates for site restore and backup

Dockerfile

chart/cluster-tasks/templates/clear-cache.yaml

chart/cluster-tasks/templates/database-restore.yaml

chart/cluster-tasks/templates/drupalsite-backup.yaml

chart/cluster-tasks/templates/drupalsite-restore.yaml

chart/cluster-tasks/values.yaml

examples/clear-cache-taskrun.yaml

examples/drupalsite-backup-taskrun.yaml

examples/drupalsite-restore-taskrun.yaml

tekton-task-templates/backup_resource.yaml

tekton-task-templates/drupal_operation_job.yaml

tekton-task-templates/restore_pv_job.yaml

velero-restic-restore/restore_pvs.sh