Missing support for the Vulkan Loader and VVL on iOS Simulator

The Vulkan SDK 1.4.357 for iOS now adds support for the Vulkan Loader and Vulkan Validation Layer (VVL) on the iOS Simulator. It achieves this via the addition of **.xcframeworks** for these iOS Vulkan libraries.

Previously, only physical iOS target libraries were provided and MoltenVK had to run standalone on the iOS Simulator without any layer support. The Vulkan Samples build system currently has this assumption baked in. With the release of SDK 1.4.357 It is now time to correct this limitation by adding support for the Vulkan Loader and VVL on the iOS Simulator.

I will submit a small PR with this change.

Start by locating the Vulkan Samples build-system logic that assumes Loader and VVL libraries are available only for physical iOS targets. Compare that logic with the SDK 1.4.357 .xcframeworks and verify the iOS Simulator build; done means the Loader and VVL are supported there without breaking physical iOS builds.

Written by the indexing model from the issue text.