[SPIR-V] support externally initialized non-floating-point column-major matrices

The following code is supported when targeting DirectX but is gated by an error when targeting spirv
https://hlsl.godbolt.org/z/zr9P6GKhx

struct A {
  RWStructuredBuffer<int3x2> Buf;
};

A a1;
A a2;

[numthreads(1,1,1)]
void main() {
  int3x2 m = a1.Buf[0];
  a2.Buf[0] = m * 2;
}

https://github.com/microsoft/DirectXShaderCompiler/blob/b87d15dbd0bca2a1ef9c9f4d957de8784ec13fe5/tools/clang/test/CodeGenSPIRV/vk.layout.non-fp-matrix.array.struct.error.hlsl#L37
https://github.com/microsoft/DirectXShaderCompiler/blob/b87d15dbd0bca2a1ef9c9f4d957de8784ec13fe5/tools/clang/test/CodeGenSPIRV/vk.layout.non-fp-matrix.error.hlsl#L19

For now marking these as not supported for the offload test suite when targeting spirv.

Start with tools/clang/test/CodeGenSPIRV/vk.layout.non-fp-matrix.array.struct.error.hlsl and tools/clang/test/CodeGenSPIRV/vk.layout.non-fp-matrix.error.hlsl, then reproduce the linked HLSL example when targeting SPIR-V. Done means externally initialized non-floating-point column-major matrices are supported for this case and the relevant test coverage reflects the accepted behavior.