[BUG]: Start Node is ignored in the Tree Picker property editor

[JoseMarcenaro]

Version 14.0.0-beta001

The issue Using the Tree Picker property editor, whatever is configured as start node is ignored.

To Reproduce Steps to reproduce the behavior:

1. Define a DataType based on Umb.PropertyEditorUi.TreePicker | Umbraco.MultiNodeTreePicker
2. Click on 'Specify Root Node'
3. Select Specific Node and pick a document in the tree
4. Save the datatype
5. Use the new DataType in a document
6. When clicking the "Choose" button, the entire content tree is displayed and any node (outside the configured start node) can be selected.