refactor: rename XR to XRSystem

chore: fix formatting
refactor: change filename and ref to xrsystem
refactor: change filename XRSystem.webidl
refactor: update crate in navigator
refactor: use XRSystem instead of XR in navigator
refactor: update Bindings.conf
refactor: use XRSystemMethods

fix: update assertions for XRSystem

fix: update manifest json

tests/wpt/mozilla/meta/MANIFEST.json

@@ -13863,7 +13863,7 @@
      ]
     ],
     "interfaces.html": [
-     "bb6adbde0b3452e6ea8f1db44941a08dbe236774",
+     "163ab416b1627e07347b83aa210712364182343a",
      [
       null,
       {}

tests/wpt/mozilla/tests/mozilla/interfaces.html

@@ -263,7 +263,6 @@ test_interfaces([
   "XMLHttpRequestEventTarget",
   "XMLHttpRequestUpload",
   "XMLSerializer",
-  "XR",
   "XRFrame",
   "XRInputSource",
   "XRInputSourceArray",
@@ -275,6 +274,7 @@ test_interfaces([
   "XRSession",
   "XRSessionEvent",
   "XRSpace",
+  "XRSystem",
   "XRView",
   "XRViewerPose",
   "XRViewport",