Proper handling of namespace in HLSL

[BenoitAmbry]

The hlsl parser fails to parse type names when they are prefixed by a namespace, for example Test::TestS ts; will fail, but TestS ts;will parse (improperly).

The following code reproduces the issue with the command line:

/usr/local/bin/glslc -x hlsl -fentry-point=pixelShader -fshader-stage=fragment --target-env=vulkan1.2 -o x.spirv ./example.hlsl

struct v2p {
    float4 p : SV_POSITION;
    float2 uv : TEXCOORD0;
    float4 c : TEXCOORD1;
};

namespace Test {
    struct TestS {
        float4 t;
        float4 v;
    };

    float4 testF(TestS ts) {
        return ts.t * ts.v;
    }

}

sampler2D MyTexture;

float4 pixelShader(v2p i) : SV_TARGET {
    Test::TestS ts; // FAILS HERE, /*Test::*/TestS ts; works, but should fail.
    ts.v = i.c;
    ts.t = tex2D(MyTexture, i.uv);
    return Test::testF(ts);
}

Note: glslc version tested:

/usr/local/bin/glslc --version
shaderc v2023.6 v2023.6
spirv-tools v2023.4 v2022.4-296-ge553b884
glslang 11.1.0-763-g76b52ebf

Target: SPIR-V 1.0