[XRI3] Fixing broken references in sample scenes in XRI3 feature bran…

…ch. (#879)

# Overview 

After updating sample scenes to the new XRI3 rig, some interactor
references broke on some test behaviours. This change fixes these
issues.

Also adjusting a game object name in the "SolverExample" scene, to
better example what the game object is.

# Fixes

-
#878
-
#877
-
#876

# Inspector/Scene Updates

### Spatial Mouse Sample Scene Changes
Updates scene to use the MRTK3/XRI3 Rig Prefab, this fixed broken
interactor references


![image](https://github.com/user-attachments/assets/d9f7f24d-ed8e-467a-9a34-b2724dc0801f)

###  Solver Examples Scene Changes
Adding hand ray interactor references on the `SolverExampleManager` test
behaviour


![image](https://github.com/user-attachments/assets/58a4b9c7-66cd-4db7-bda1-d3c52f07a753)

### Eye Tracking Visualizer Example Scene Changes
Adding gaze interactor references on the `LogStructureEyeGaze` test
behaviour.


![image](https://github.com/user-attachments/assets/f0154bd6-6530-4dc3-b7d5-bed9d4fbeaf2)