Make Unique (Recursive) Doesn't Work For AnimationTree BlendTree Resources

### Tested versions

v4.2.2.stable.official [15073afe3]

### System information

Godot v4.2.2.stable - Windows 10.0.22631 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 4070 SUPER (NVIDIA; 32.0.15.5612) - Intel(R) Core(TM) i7-14700KF (28 Threads)

### Issue description

When using the "Make Unique (Recursive)" option on AnimationTree Tree Root resource as AnimationNodeBlendTree, subresources (i.e., the nodes currently in the tree) are not made unique, even though they show up in the recursive option popup window (and are checked).

### Steps to reproduce

1. Add AnimationTree to scene
2. Add AnimationNodeBlendTree as Tree Root resource
3. Add a node (i.e., animation) and set a parameter
4. Duplicate the AnimationTree
5. Click the drop down on the Tree Root resource and click "Make Unique (Recursive)"
6. Ensure all items are checked and hit okay
7. Change the parameter in the added node
8. Go back to the first AnimationTree and see that it changed as well

### Minimal reproduction project (MRP)

[New Game Project.zip](https://github.com/user-attachments/files/16344108/New.Game.Project.zip)

Start with the attached New Game Project.zip and reproduce the issue using the listed AnimationTree and AnimationNodeBlendTree steps. Trace the editor's Make Unique (Recursive) handling for the AnimationTree Tree Root and its child nodes, then verify that changing a parameter in the duplicated tree no longer changes the original.

Written by the indexing model from the issue text.