Remove deprecated WebVR

[RaananW]

This PR removes all traces of WebVR from the engine.
The only thing that was left is the VR Experience helper. This will prevent from old code using the experience helper to stop working, and WebXR will be used as a fallback.

[bjsplat]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s).
To prevent this PR from going to the changelog marked it with the "skip changelog" label.

[bjsplat]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s).
To prevent this PR from going to the changelog marked it with the "skip changelog" label.

[RaananW]

Fixes #11128

[RaananW]

The next task would probably be #13831

[bjsplat]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s).
To prevent this PR from going to the changelog marked it with the "skip changelog" label.

[bjsplat]

Snapshot stored with reference name:
refs/pull/14439/merge

Test environment:
https://babylonsnapshots.z22.web.core.windows.net/refs/pull/14439/merge/index.html

To test a playground add it to the URL, for example:

https://babylonsnapshots.z22.web.core.windows.net/refs/pull/14439/merge/index.html#WGZLGJ#4600

Links to test babylon tools with this snapshot:

https://playground.babylonjs.com/?snapshot=refs/pull/14439/merge
https://sandbox.babylonjs.com/?snapshot=refs/pull/14439/merge
https://gui.babylonjs.com/?snapshot=refs/pull/14439/merge
https://nme.babylonjs.com/?snapshot=refs/pull/14439/merge

To test the snapshot in the playground with a playground ID add it after the snapshot query string:

https://playground.babylonjs.com/?snapshot=refs/pull/14439/merge#BCU1XR#0