Fix hardcoded unused struct members

[mikes-lunarg]

safe_struct_generator.py uses a hardcoded list of unused struct members so it can determine if a pointer is safe to follow

Vulkan-Utility-Libraries/scripts/generators/safe_struct_generator.py

Lines 87 to 91 in 70a16b0

	# TODO: Hook this up to the member deprecation in the XML so it can be automatically updated
	self.unused_params = {
	'VkDeviceCreateInfo':
	['ppEnabledLayerNames', 'enabledLayerCount'],
	}

It would be better if vulkan_object exposed the deprecated xml attribute so we don't have to keep this list up to date

            <member noautovalidity="true" deprecated="unused"><type>uint32_t</type>               <name>enabledLayerCount</name></member>
            <member noautovalidity="true" deprecated="unused">const <type>char</type>* const*      <name>ppEnabledLayerNames</name><comment>Ordered list of layer names to be enabled</comment></member>

[spencer-lunarg]

deprecated="unused" seems fragile as we have the <deprecate> tag and I feel someone will probably ask to change all of this... will keep eye out, if a 2nd unused comes, I will make sure to get something in VulkanObject