Functional changes:
- Enable only actually used features, as drivers may take more optimal
paths when certain features are disabled.
- Support VK_SAMPLER_ADDRESS_MODE_CLAMP_TO_EDGE.
- Fix the separateStencilMaskRef check doing the opposite.
- Support shaderRoundingModeRTEFloat32.
- Fix vkGetDeviceBufferMemoryRequirements pointer not passed to the Vulkan
Memory Allocator.
Stylistic changes:
- Move all device extensions, properties and features to one structure,
especially simplifying portability subset feature checks, and also making
it easier to request new extension functionality in the future.
- Remove extension suffixes from usage of promoted extensions.
