Missing documentation and assertion for required resource Initialization in latest FSR version

[PanosK92]

In the latest version of FSR, the function ffxFsr3UpscalerGetSharedResourceDescriptions must be called to retrieve the necessary resource descriptions, after which the corresponding textures need to be manually created. This step seems to be a new requirement, but it's neither mentioned in the changelog nor documented on GPUOpen.

Context: https://github.com/PanosK92/SpartanEngine/blob/e47b73aadb7a3a9bd14685db7a1e949d3fa8f544/runtime/RHI/Vulkan/Vulkan_FidelityFX.cpp#L734

If you don't do that, and you simply upgrade to the latest FSR, you'll crash. The crash is generic and doesn't provide helpful context. I believe this could be improved in two ways:

• Documentation update: Please add a note in the changelog or on GPUOpen to inform developers that they must now initialize these resources manually.
• Runtime assertion: Implement an assert that checks if any of the shared resources are null, clearly indicating that these resources must be initialized. This would clarify the setup requirements for developers.