HLSL: various SPIR-V compute shader IDs must be a 3-vector of integers.

This PR forces the external definition of SV_GroupID variables to 3-vectors.
The conversion process between the shader-declared type and the external type
happens in wrapped main IO variable conversion.

The same applies to SV_DispatchThreadID and SV_GroupThreadID.

Fixes: #1371

gtests/Hlsl.FromFile.cpp

@@ -195,6 +195,7 @@ INSTANTIATE_TEST_CASE_P(
         {"hlsl.hull.void.tesc", "main"},
         {"hlsl.hull.ctrlpt-1.tesc", "main"},
         {"hlsl.hull.ctrlpt-2.tesc", "main"},
+        {"hlsl.groupid.comp", "main"},
         {"hlsl.identifier.sample.frag", "main"},
         {"hlsl.if.frag", "PixelShaderFunction"},
         {"hlsl.imagefetch-subvec4.comp", "main"},