Vulkan: Add dedicated memory bit to external memory pool

This ensures memory has offset zero, makes it easier to share.

Pull Request: https://projects.blender.org/blender/blender/pulls/137363

source/blender/gpu/vulkan/vk_device.cc

@@ -250,6 +250,7 @@ void VKDevice::init_memory_allocator()
                                          nullptr,
                                          VK_IMAGE_LAYOUT_UNDEFINED};
   VmaAllocationCreateInfo allocation_create_info = {};
+  allocation_create_info.flags = VMA_ALLOCATION_CREATE_DEDICATED_MEMORY_BIT;
   allocation_create_info.usage = VMA_MEMORY_USAGE_AUTO;
   uint32_t memory_type_index;
   vmaFindMemoryTypeIndexForImageInfo(