Ambari is a cluster provisioning tool to install and manage various Apache projects like HDFS, YARN, Zookeeper or Kafka. Ambari has a concept of a stack definition which is used by both Pivotal and Hortonworks. The stack definition is usually made up of components supported by the maintainer.
Spring XD is not part of the main Ambari distribution for PHD or HDP. However, it is easy to extend an existing Ambari installation via a simple RPM installation which modifies existing stack definitions.