Support reconfigure operation

We currently have no equivalent of [`ZookeeperAdmin.reconfigure()`](https://zookeeper.apache.org/doc/r3.8.1/apidocs/zookeeper-server/org/apache/zookeeper/admin/ZooKeeperAdmin.html#reconfigure-java.lang.String-java.lang.String-java.lang.String-long-org.apache.zookeeper.data.Stat-) ([`concept docs`](https://zookeeper.apache.org/doc/r3.8.1/zookeeperReconfig.html#ch_reconfig_api)).