CMake: Added separate Vulkan-Hpp target alongside Vulkan-HppModule with propagating compile definitions

[M2-TE]

The Vulkan-Hpp headers have numerous compile definitions for configuration, which can of course be done manually, but it is much nicer to have actual support for them in CMake via option().
This is particularly true for the C++20 module, which requires compile definitions at the configure stage due to the lack of preprocessor stuff with #include.
Projects relying on Vulkan (e.g. the VulkanMemoryAllocator) can also consume these propagating compile definitions to not have to define them multiple times.

To this end, I made some changes to the CMakeLists.txt, similar to what is now in the Vulkan-Hpp repository, to provide three separate targets with consolidated naming:

• Vulkan-Headers ALIAS Vulkan::Headers: Same as before, so it will not break anything.
• Vulkan-Hpp ALIAS Vulkan::Hpp: Separated from Vulkan-Headers, as to provide isolated compile definitions for this C++ target, even though it shares the same interface include directory as the C target.
• Vulkan-HppModule ALIAS Vulkan::HppModule: Consumes Vulkan-Hpp and its compile definitions. Adjusted naming to match the names of the repository and other targets. Added errors for mismatching compilers (previously warning) and CMake versions. Added ability to build the C++20 module with import std; (as this is still a very experimental feature for most compilers, I have not updated the compiler requirements for it).

Currently, the VK_NO_PROTOTYPERS and VULKAN_HPP_DISPATCH_LOADER_DYNAMIC options are separated as per their respective compile definitions, but it might make sense to consolidate both into a single option to enable the respective C/C++ flag in the two targets.

[CLAassistant]

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