[HLSL][SPIRV] Handle resource `Load(int, out uint)` and `CheckAccessFullyMapped` when targeting SPIR-V

[s-perron]

All of the HLSL buffer (and texture) types have overloads of Load like RWBuffer::Load(int, out uint). We have implementations of these using builtins, but the builtins are currently only handled correctly for DirectX.

DXC maps these loads to OpImageSparseRead, and uses OpImageSparseTexelsResident on the resulting status for CheckAccessFullyMapped. Note that in DirectX we've implemented the Load function as-if it calls CheckAccessFullyMapped implicitly, which I believe also matches the behaviour of DXC, and thus we've implemented CheckAccessFullyMapped as simply a cast from uint to bool. I haven't looked into whether this makes sense for SPIR-V too.

[bob80905]

I'm changing this issue, it's no longer going to be about implementing a SPIR-V intrinsic, since that is no longer going to be the route we go down. Instead, this issue should just be about implementing the SPIR-V side of the status overload of load.