delegate features.

* `tf.data`
    * Add `wait` to `tf.data.Dataset.load`. If `True`, for snapshots written
      with `distributed_save`, it reads the snapshot while it is being written.
      For snapshots written with regular `save`, it waits for the snapshot until
      it's finished. The default is `False` for backward compatibility. Users of
      `distributed_save` are recommended to set it to `True`.

 - All StorageClass parameters for volume provisioning are supported.
 - All features supported with PersistentVolumeClaims are supported, such as storage capacity tracking, snapshots and restore, and volume resizing.

### Immutable Secrets and ConfigMaps (beta)