Fixed issue that broke the camera background rendering when URP post-processing was enabled on the AR camera.
The documentation for the `ARFace` scripting API for accessing left eye, right eye, and fixation point incorrectly referred to a nullable value type, when in fact the returned type is a Transform. This has been fixed.
Added script updater support for facilitating the rename of Reference Points to Anchors.
Added `FormerlySerializedAs` to `ARAnchorManager.m_AnchorPrefab` field to preserve any prefab specified when it was the `ARReferencePointManager`.
Patched a memory leak by destroying the camera textures when the camera manager is disabled.
Eliminating shader compiler errors that started with Unity 2020.1 and that originate from the ARKit package.
