[XR] Update to latest versions of ARFoundation, ARCore, and ARKit packages

Packages/manifest.json

 {
   "dependencies": {
-    "com.unity.xr.arcore": "1.0.0-preview.17",
-    "com.unity.xr.arkit": "1.0.0-preview.12",
-    "com.unity.xr.arfoundation": "1.0.0-preview.13"
+    "com.unity.xr.arcore": "1.0.0-preview.18",
+    "com.unity.xr.arkit": "1.0.0-preview.13",
+    "com.unity.xr.arfoundation": "1.0.0-preview.14"
   }
 }