VK_KHR_portability_subset device extension missing in [hpp_]hello_triangle[*] samples

[SRSaunders]

I'm not sure how I missed this before, but the VK_KHR_portability_subset device extension is missing for the hello_triangle, hpp_hello_triangle, and hello_triangle_1_3 samples. It *is* present in the general framework for other samples, but somehow I forgot to add it to these standalone samples.

The spec says that VK_KHR_portability_subset must be enabled if available in the implementation. Leaving it out leads to validation errors on macOS/iOS when the validation layer is enabled:

[error] 976972960 Validation Layer: Error: VUID-VkDeviceCreateInfo-pProperties-04451: Validation Error: [ VUID-VkDeviceCreateInfo-pProperties-04451 ] Object 0: handle = 0x600000270200, type = VK_OBJECT_TYPE_PHYSICAL_DEVICE; | MessageID = 0x3a3b6ca0 | vkCreateDevice(): VK_KHR_portability_subset must be enabled because physical device VkPhysicalDevice 0x600000270200[] supports it.
The Vulkan spec states: If the VK_KHR_portability_subset extension is included in pProperties of vkEnumerateDeviceExtensionProperties, ppEnabledExtensionNames must include "VK_KHR_portability_subset" (https://vulkan.lunarg.com/doc/view/1.4.304.0/mac/1.4-extensions/vkspec.html#VUID-VkDeviceCreateInfo-pProperties-04451)

I will submit a PR to fix.