Need to validate that Location is only applied to things that are allowed to have locations

The latest SPIR-V spec currently says of the Location decoration:

> Only valid for the **Input**, **Output**, and **UniformConstant** Storage Classes.

However, the NV_ray_tracing extension also uses it for ray payloads and callable data which have their own storage classes. This bug is being fixed by https://github.com/KhronosGroup/SPIRV-Registry/pull/80. However, to my knowledge, SPV_NV_ray_tracing shaders aren't failing validation so there is a validation check missing here.

Start by locating the validator logic for the Location decoration and the SPV_NV_ray_tracing handling of ray payload and callable data storage classes. Compare the accepted storage classes with the specification and the referenced SPIR-V Registry change; done means validation correctly enforces the allowed cases without rejecting the extension's valid uses.

Written by the indexing model from the issue text.