VK_EXT_descriptor_indexing extension is enabled.
- Change MVKConfiguration::useMetalArgumentBuffers to enum instead of boolean
and default to enabling Metal argument buffers for VK_EXT_descriptor_indexing.
- Leave Metal argument buffers disabled by default until they are improved.
- Enable VkPhysicalDeviceVulkan12Features::descriptorIndexing.
- Add MVKPhysicalDeviceVulkan12FeaturesNoExt to track and enable Vulkan 1.2
features not part of any prior extensions absorbed by Vulkan 1.2.
- Update VK_MVK_MOLTENVK_SPEC_VERSION to version `36`.
- MVKDeviceTrackingMixin remove unnecessary inline declarations.
- MoltenShaderConveter tool support Metal Argument Buffers and MSL 3.0.