hand-controls: rotates models to match WebXR definition (fix #4848)

[DougReeder]

Description:
Fixes #4848
The WebXR standard now defines the grip space such that a cylinder held in a closed hand points along the Z axis. The models currently have such a cylinder point along the X-Axis.

Changes proposed:
There are two approaches

1. rotate the mesh in code, as done here
2. edit the GLB files

I'm fine with either, but I lack knowledge of 3D tools (such as Blender) to implement the second approach.

[DougReeder]

Documentation: https://developer.mozilla.org/en-US/docs/Web/API/WebXR_Device_API/Inputs#facing_and_targeting

[dmarcos]

Thanks!. I think we have to check for sceneEl.hasWebXR before applying the offset so WebVR (Firefox) still works as before.

I would also add a comment in the offset:

// The WebXR standard defines the grip space such that a cylinder held in a closed hand points along the Z axis. ./
// The models currently have such a cylinder point along the X-Axis.
var modelOrientationXOffset = sceneEl.hasWebXR ? xxx : 0;
...

[dmarcos]

Thank you!