Migration to 2.2.0

Remove Standard and Built-In Tree Nodes XML

All built-in MoveIt Studio and BehaviorTree.CPP behaviors are now specified from included node model XML files. There is no longer a need to maintain the standard_tree_nodes_model.xml or tree_nodes_model.xml files in your objectives directory. For more information refer to the public user workspace, and to the documentation on built-in MoveIt Studio behaviors in the List of Core Behaviors.