Inconsistent "Mock HMD Loader" naming in the "Project Settings"

Steps to reproduce:

1. Create a project
2. Go to "Edit" -> "Project Settings"
3. Select the "XR Plug-in Management" item
4. Click the "Install XR Plugin Management" button in the "XR Plugin Management" window
5. Check "Unity Mock HMD" in the "Plug-in Providers" section
6. Observe the checked "Unity Mock HMD" item in the "Plug-in Providers" section and the newly displayed "MockHMD" in the "Project Settings" list

Actual results: Inconsistent "Mock HMD Loader" naming

Expected results: The same consistent naming should be used in all places

Reproducible with versions: 1.5.0-exp.1(6000.5.0a3)

Tested on (OS): macOS - Tahoe 26.1