Parent node for all created WebXR nodes

[darkverse]

Feature request

• as discussed on the forum here: https://forum.babylonjs.com/t/webxr-keepassets-and-assetcontainers
• WebXR currently creates nodes, such as controllers at the root level, when trying to use in conjunction with KeepAssets and scene switching/AssetContainers it would be easier to maintain, and would be overall neater anyway, if all WebXR created nodes/objects were parented to a WebXR_root TransformNode (say).

[github-actions[bot]]

This issue has been automatically staled because it has been inactive for more than 14 days. Please update to "unstale".

[thomlucc]

https://forum.babylonjs.com/t/parent-node-for-all-created-webxr-nodes/52148