The `LegacyTreeDef` type and its normalization path have been removed.
All tree definitions must now use the factory functions (`leaf`,
`sequential`, `parallel`, `selector`, `random`, `repeat`). The
`TreeDef` type is now simply `TaskEntityDef`.
Add `leaf`, `sequential`, `parallel`, `selector`, `random`, and `repeat`
functions that return `EntityDef` trees. Legacy object definitions are
still
accepted for backward compatibility. Non-task child entities are ignored
by
the runner, and `buildTree` now stores the root entity on
`TaskRunner.root`.
hyper