code : normalize enum names (llama/5697)

Introduce backend GUIDs (ggml/743)

Refactor validation and enumeration platform checks into functions to clean up ggml_vk_instance_init()

Add check for VK_KHR_portability_enumeration for MoltenVK support

Add preprocessor checks for Apple devices.

Resolve ErrorIncompatibleDriver with Vulkan on MacOS.

cmake : fix VULKAN and ROCm builds (llama/5525)

vulkan: Find optimal memory type but with fallback (llama/5381)

vulkan: only use M-sized matmul on Apple GPUs (llama/5412)

src : relocate new backend sources