This release features a new ratified graphics API binding extension,
XR_KHR_metal_enable, including support in hello_xr. The loader test has
had substantial improvements as well. There are also an assortment of
smaller fixes and improvements.

-   Registry
    -   Add: New ratified Khronos extension: XR_KHR_metal_enable.
        (internal MR 2721)
    -   Chore: Reserve 15 extension id numbers for ByteDance. (internal
        MR 3409)
    -   Fix: Clarified that views in XR_VARJO_quad_views needs to have
        identical poses for each eye. (internal MR 3396)
    -   Fix: Add missing interaction profile extensions for OpenXR 1.1
        promoted Meta interaction profiles. (internal MR 3398)
    -   Fix: Correctly mark the Magic Leap home button as a system
        button in the XML. (internal MR 3405)
    -   Fix: Add XR_ERROR_VALIDATION_FAILURE to all functions from
        XR_EXT_conformance_automation. (internal MR 3417)
-   SDK
    -   API dump layer: Improvement: Move a non-generated function out
        of the Python- generated source file. (internal MR 3336)
    -   API dump layer: Improvement: Clean up usage of RAII mutex lock
        guards. (internal MR 3336)
    -   Layers and loader: Improvement: Disambiguate
        XrGeneratedDispatchTable between loader and API layers.
        (internal MR 3406)
    -   Loader test: Improvement: Migrate to use Catch2 (matching the
        CTS) instead of an ad-hoc test framework. (internal MR 3337)
    -   hello_xr: Add: Metal graphics plugin (use -g Metal) for running
        it on macOS with XR_KHR_metal_enable extension. (internal MR
        3009, internal MR 3456)
    -   hello_xr: Improvement: Use XrMatrix4x4f_CreateFromRigidTransform
        in place of XrMatrix4x4f_CreateTranslationRotationScale for
        known rigid transforms. (internal MR 3349)

Note: There is no 1.1.39 release: it was skipped to keep the monthly
patch version increment cadence given the lack of a release in July.

GitOrigin-RevId: 3ec99b59aaf8ac8d7c8d822ddd174fc6c0c5e57b