The VK_MVK_moltenvk extension has never been brought inside Vulkan, and
the functions have never been supported by the Vulkan Loader and Layers.
Most of the functionality has long been replaced by the official
VK_metal_objects extension.
- Remove VK_MVK_moltenvk as an advertised extension.
- Refactor vk_mvk_moltenvk.h header file into separate headers files:
- mvk_config.h - Valid public config functions
- mvk_private_api.h - Valid development debugging functions used with care
- mvk_deprecated_api.h - Formally deprecated functions.
- Retain skeleton vk_mvk_moltenvk.h header file for legacy compatibility only.
- Update documentation and header comments to explain changes.