Enable configuration to select backup deletion mechanism

Way back in https://github.com/kopeio/etcd-manager/issues/325 it was observed that object versioning and deleting the object (which actually means creating a deletion marker in a versioned bucket) can create large storage costs as the backups are not removed by etcd. However, in a bucket with S3 Object Lock enabled, it typically not possible to delete a version until its lock is released. For users in this situation, using regular S3 delete (which creates the delete marker) and then using S3 lifecycle to manage actually deleting the version is pretty desirable. This manifests very similarly to https://github.com/kubernetes/kops/issues/14031, where the cost of the tier 1 operations that are trying to delete objects gets very high.