Refactor structure initializers

[robbiesri]

Right now, we follow this pattern in the app code:

VkDeviceCreateInfo device_ci = {
  VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO,
};

To be more clear (and safe), we should do one of these two patterns instead.

VkDeviceCreateInfo device_ci = {
  .stype = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO,
};

VkDeviceCreateInfo device_ci = {};
device_ci .stype = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO;