[WebXR] WebXR should base its foveation on the app's setting
<rdar://problem/125824522>
Pull request: https://github.com/WebKit/WebKit/pull/26773
Committed 277037@main (4d12bc5c1a01): <https://commits.webkit.org/277037@main> Reviewed commits have been landed. Closing PR #26773 and removing active labels.