Replace the old Desert sample scene

[De-Panther]

The desert sample scene is still there since the Mozilla WebVR era.
It's good for basic VR demo, but less for more complex VR features or AR features.

We need a scene that would be able to show:

• As much VR features as it can.
• As much AR features as it can.
• Switching between VR and AR on supported devices.

A lab might be a good option.

[De-Panther]

In addition to the desert scene, there's now XR Interaction Toolkit sample.
Once there'll be full support for the Input System and the XR Interaction Toolkit, including performance fixes, we'll be able to remove the old Desert sample.